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Thunderbird log file appears to not show all steps to server access error.

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  • Paskiausią atsakymą parašė Toad-Hall

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I recently updated to Windows 11. I decided to switch to Thunderbird because of its very good POP3 support. I value the ability to download, organize and access my email offline. I installed Thunderbird 91.6.1. I setup an SSL secure connection with normal password authentication for both my ISPs POP3 and SMTP server using the ISPs recommended settings and port number. I can successfully download my emails, but when I try to send email I get Thunderbird error message 'The message could not be sent because the connection to outgoing server (SMTP) mail.ISP.ca was lost in the middle of the transaction. As part of troubleshooting, I changed the outgoing server connection security setting to 'None', the authentication method is then restricted to 'Password, transmitted insecurely' (against my ISPs recommendation), but with these settings I was able to send email successfully. After reading some of the Thunderbird support docs, I learned that I could turn on a logging function. I created a Windows .bat file containing the following commands:

set MOZ_LOG=POP3:5,SMTP:5,timestamp set MOZ_LOG_FILE=%USERPROFILE%\Desktop\Thunderbird.log "%ProgramFiles%\Mozilla Thunderbird\thunderbird.exe"

I executed the mbat file and then repeated the email send using the secure SMTP connection. In the log I see Thunderbird sending the following commands and the corresponding response from the SMTP server:

1 Thunderbird SEND: CAPA (a request to SMTP server for a list of CAPAbilities it supports) 2. SMTP server responds with list 3. Thunderbird sends my user name 4. Thunderbird SEND: AUTH PLAIN (Thunderbird sends my password) 5. SMTP server responds with login succeeded 6. Thunderbird SEND: STAT (a request to SMTP server for the number of emails in my inbox) 7. SMTP server responds that there are 148 8. Thunderbird SEND: LIST (a request to SMTP server for a summary of the messages) 9. SMTP server responds with a message number and the corresponding length of each message (1-48) 10. Thunderbird SEND: UIDL (a request to SMTP server for a unique identifier for each message) 11. The SMPT server responds with the identifiers but the log cuts off at 179 . . 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] RECV: 178 XXXXXXXXXXXXXXXGobbledygookXXXXXXXXXXXXXXXXXXXXX 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] Entering state: 12 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] RECV: 179 XXXXXXXXXXXXMoreGobbledygookXXXXXXXXXXXXXXXXXXXXX 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] Entering s

12. Thunderbird issues the connection lost message.

As you can see, the log appears to be cutoff after the id info sent for email 179. I had expected that if the cutoff was due to the connection disconnect, the disconnect would have had a log entry. So I am left with the thought that there is a bug in the logging function, or maybe that the remainder of the log was in cache and is never sent to the console. It would really be useful in my troubleshooting of this problem to see a complete log of the activity right to the connection failure. So my questions: Is the log cutoff normal? Are there any other parameters for the log function that I have missed?

I recently updated to Windows 11. I decided to switch to Thunderbird because of its very good POP3 support. I value the ability to download, organize and access my email offline. I installed Thunderbird 91.6.1. I setup an SSL secure connection with normal password authentication for both my ISPs POP3 and SMTP server using the ISPs recommended settings and port number. I can successfully download my emails, but when I try to send email I get Thunderbird error message 'The message could not be sent because the connection to outgoing server (SMTP) mail.ISP.ca was lost in the middle of the transaction. As part of troubleshooting, I changed the outgoing server connection security setting to 'None', the authentication method is then restricted to 'Password, transmitted insecurely' (against my ISPs recommendation), but with these settings I was able to send email successfully. After reading some of the Thunderbird support docs, I learned that I could turn on a logging function. I created a Windows .bat file containing the following commands: set MOZ_LOG=POP3:5,SMTP:5,timestamp set MOZ_LOG_FILE=%USERPROFILE%\Desktop\Thunderbird.log "%ProgramFiles%\Mozilla Thunderbird\thunderbird.exe" I executed the mbat file and then repeated the email send using the secure SMTP connection. In the log I see Thunderbird sending the following commands and the corresponding response from the SMTP server: 1 Thunderbird SEND: CAPA (a request to SMTP server for a list of CAPAbilities it supports) 2. SMTP server responds with list 3. Thunderbird sends my user name 4. Thunderbird SEND: AUTH PLAIN (Thunderbird sends my password) 5. SMTP server responds with login succeeded 6. Thunderbird SEND: STAT (a request to SMTP server for the number of emails in my inbox) 7. SMTP server responds that there are 148 8. Thunderbird SEND: LIST (a request to SMTP server for a summary of the messages) 9. SMTP server responds with a message number and the corresponding length of each message (1-48) 10. Thunderbird SEND: UIDL (a request to SMTP server for a unique identifier for each message) 11. The SMPT server responds with the identifiers but the log cuts off at 179 . . 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] RECV: 178 XXXXXXXXXXXXXXXGobbledygookXXXXXXXXXXXXXXXXXXXXX 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] Entering state: 12 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] RECV: 179 XXXXXXXXXXXXMoreGobbledygookXXXXXXXXXXXXXXXXXXXXX 2022-02-24 08:31:51.297000 UTC - [Parent 3492: Main Thread]: I/POP3 [this=148cfb92400] Entering s 12. Thunderbird issues the connection lost message. As you can see, the log appears to be cutoff after the id info sent for email 179. I had expected that if the cutoff was due to the connection disconnect, the disconnect would have had a log entry. So I am left with the thought that there is a bug in the logging function, or maybe that the remainder of the log was in cache and is never sent to the console. It would really be useful in my troubleshooting of this problem to see a complete log of the activity right to the connection failure. So my questions: Is the log cutoff normal? Are there any other parameters for the log function that I have missed?

Modified by muse2u

Chosen solution

re : I used the mxtoolbox link to check the IP address assigned by the ISP and it indicates that it does have a reverse DNS but it also indicates that it is on blacklists: SORBS DUHL Spamhaus Zen

ZEN is the combination of all Spamhaus IP-based DNSBLs into one single powerful and comprehensive blocklist to make querying faster and simpler. It contains the SBL, SBLCSS, XBL and PBL blocklists.

As the info implies you may be on a blocklist then it is worth to try to get your IP address taken off the various spamhaus SBL, SBLCSS, XBL and PBL blocklists:

there is information at that website on how to go about removal.


If you currently have a POP account and you are thinking of removing it in order to create an imap account: Create folders in the 'Local Folders' mail account and get copis of emails moved from POP into Local Folders before removing the Pop account from via Account Settings.

re :Does Thunderbird allow me to say, create a 'Local Storage Folder' with subfolders for organizing/archiving different categories/subjects/senders, etc.., and the copies do not get deleted when the originals get deleted from the IMAP account?

Thunderbird has a default mail account called 'Local Folders'. You can create folders in that 'Local Folders' mail account. Emails copied from an imap folder into a 'Local Folders' mail account folder do not synchronise with server. They are stored on your computer.

You can create an imap account and set up to download/synchronise all subscribed folders. You can create folders in an imap account and they will get created on the server OR you can create folders in the webmail account and subscribe to see them. You can choose to downoad full copies of emails into the imap folders.

Once you have an imap account, you can use : Menu app icon > File > Offline > Download/sync now Select checkbox: 'Mail Messages' Select checkbox: 'Work Offline once download and/or synchronisation is complete'

the 'Select..' button offers you the opportunity to check all folders are selected for full copy download. Once all set up click on 'OK'

download.Sync occurs and then Thunderbird goes into Offline mode. Going into Offline mode means no connection to server, so when coping a lot of batches of emails from an imap folder into the 'Local Folders' folders, no folder is connecting to server, so less chance of something going wrong.

suggest you always use the right click on highlighted emails >'Copy to' option because if something goes wrong the original still exists. If you can read emails in the 'Local Folders' folders you know you have a good copy.

You can easilly go back to 'Online' mode by clicking on the Offline/Online icon located far left in bottom 'Status bar'

When you perform a backup of the 'Thunderbird' folder containing Profiles to an external drive, everything is backed up. Remember you must exit Thunderbird before performing a backup. Backup 'Thunderbird' folder is: C://Users/Username/Appdata/Roaming/Thunderbird

Info on imap, synchronisation etc links:

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All Replies (9)

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SMTP logging in V91 uses the error console. I tried to address a how to here https://thunderbirdtweaks.blogspot.com/2021/10/logging-mail-sending-in-thunderbird.html

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Matt: Thank you for your assistance. I followed the instructions in the Sep. 2021 post. I used the Config Editor to set the preference mailnews.smtp.loglevel to All, opened the Error Console, cleared it, set logging to All and performed a mail send in Thunderbird and then monitored the log. The log showed the send error as follows:

mailnews.smtp: Sending message <xxxgobbledygookxxx@ISP.ca> SmtpService.jsm:84:18 mailnews.smtp: Connecting to smtp://mail.ISP.ca:587 SmtpClient.jsm:121:17 mailnews.smtp: Connected SmtpClient.jsm:386:17 mailnews.smtp: error { target: TCPSocket, isTrusted: true, name: "NetworkInterruptError", message: "Network", errorCode: 2152398919, srcElement: TCPSocket, currentTarget: TCPSocket, eventPhase: 2, bubbles: false, cancelable: false, … } SmtpClient.jsm:433:17 mailnews.send: Sending failed; The message could not be sent because the connection to Outgoing server (SMTP) mail.shaw.ca was lost in the middle of the transaction. Try again., exitCode=2153066799, originalMsgURI= MessageSend.jsm:332:27 mailnews.smtp: Closing connection... 2 SmtpClient.jsm:152:17 mailnews.smtp: Socket closed. SmtpClient.jsm:486:17

This is the kind of output I was hoping to see. I will try to interpret the error codes to see if they give me more of an explanation of what is happening.

The post you made in Sep. also suggested comparing the log output of current mail sending code vs old code to determine if the new code was the cause of a problem. Using the Config Editor, I set the preference mailnews.smtp.jsmodule to false, and repeated the mail send. The send failed again, this time with the following log:

mailnews.send: Sending failed; The message could not be sent because the connection to Outgoing server (SMTP) mail.shaw.ca was lost in the middle of the transaction. Try again., exitCode=2153066799, originalMsgURI= MessageSend.jsm:332:27 NS_ERROR_UNEXPECTED: Component returned failure code: 0x8000ffff (NS_ERROR_UNEXPECTED) [nsIMsgMailNewsUrl.server] alertHook.jsm:49

I have read in some of the online documentation that this error can be caused by a security program/function of the computer interrupting the data stream from the SMTP server. I followed that by performing the Thunderbird mail send in Windows Safe Mode without any security program running with the same results.

There were also suggestions that the Windows 11 update enables both IPv6 and IPv4 by default and that IP v6 could be an issue. I disabled IPv6 and ran the mail send in Thunderbird with the same failure.

I also set up Microsoft Windows Mail with the same POP3/SMTP server settings and was able to send/receive mail. But I have no interest in using the Microsoft program for my POP3 emailing.

The Sep. post refers to a Thunderbird v93? Am I running backlevel? Is there a higher version of Thunderbird, beta, that may have a fix for this issue?

I really like what I see in Thunderbird and eager to use for my email needs. I willing and able to try any beta version available to assist you and your team.

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I'm wondering if this is to do with Shaw not liking your password. Perhaps it has not been recently updated or is what Shaw deem as 'weak'.

I located this info:

Old and/or Weak email passwords can limit how many emails you can send and lead to hacked accounts. See How to create secure email passwords for more information.

The info says: The best practice for creating a secure password is for your password to meet all of the criteria listed below:

8 or more characters in length, but the longer the password is, the better.

Include ALL, not just some, of the following four character types:

  • Lowercase letters
  • Uppercase letters
  • Numbers
  • Symbols
  • Obvious substitutions, such as '@' for 'A' or '3' for 'E', are not considered strong and should be avoided.
  • Avoid personal details like important dates, phone numbers, addresses, and family names.
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Toad-Hall: I reviewed both the pages you referred to me. The password that I use does meet the guidelines recommended by you and the ISP. The same password was also used in the Windows Mail test successfully. I found the troubleshooting page interesting. They suggested sending an email to yourself as a test and doing that on a direct connection to their WAN. All my tests were done from my home LAN which has a direct connection with the ISP and all of my tests were emails either to myself or my wife and both of us are on their email server. I will follow some of the other suggestions on that page. At this point, I think you and Matt have addressed my original request, a clarification of the Thunderbird logging facility. The introduction to the Error Console provided me with another tool to help me troubleshoot my Thunderbird problem. Not sure what else I can do. If Mozilla support would like me to flag my original problem as being solved I can do that. Thank you for your support.

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Have a look at the SMTP settings you are using.

The Shaw server does not send any encryption certificates, so if you have connection security set to anything but none or the authentication set to anything but normal password something will give and this lost connection may be it. https://www.immuniweb.com/ssl/mail.shaw.ca/Kein6Bd1/

I also was looking here https://support.shaw.ca/t5/internet-discussions/cannot-send-email-via-smtp-appears-to-be-shaw-s-cloudfilter/td-p/45816 which sounds a lot like what you were mentioning so may be the same thing.

The reference to a reverse lookup might make it worth checking here with your IP address. https://mxtoolbox.com/ReverseLookup.aspx

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Matt: Another good set of tools. Your observation of the lack of encryption certificate using the immuniweb site is something I have seen recently when I was troubleshooting Microsoft Live Mail. I have been using Live Mail for many years. I wanted the ability to download my mail and organize it in local folders, access it offline, and subsequently archive it. I have important personal and business email that I can reference as far back as 2003. My email's access is not at the whim of some obscure email service provider's existence but under my responsibility, privacy and protection. Live Mail provided me with that ability. Even after Microsoft dropped support and made it difficult to install in subsequent Windows updates, I persevered and was able to continue to use it until the Windows 11 update. During the update a program module was replaced and Windows Live Mail lost an API access point that it needed. During troubleshooting of that issue, I came across the ISP mail server settings. They were different from what they had been recommending for years. The focus was now on security and authentication. I made those changes (secure connection and password authentication) and that was when I ran across the server missing certificate warning. Windows Live reaction was a little different from Thunderbird. Windows Live identified that the mail server (the message did not specify if it was the POP3 or SMTP) lacked a certificate but then gave me the option of continuing to access the server regardless. I don't understand what technical changes Windows Live did to make the connection work (probably initiated an unsecured connection), but it was able to proceed to perform a mail download. Unfortunately I was not able to resolve the missing API issue and decided it was time I accepted the fact that I had to find a more current email program that would allow me to download my email and organize/access it locally. After some research I concluded that Thunderbird was the best option. In conclusion, if the server(s) are lacking a certificate that is required for a secure connection, it would appear that the ISPs mail server setting recommendations are irrelevant and a secure connection may be unachievable.

I had a look at the Shaw email user who reported problems sending authenticated SMTP email. The symptoms are similar. He is reporting issues when not on a Shaw internet connection. All my mobile devices are using IMAP secure SSL password connections and are having no send/receive issues anywhere outside of my home. My problem is on a single desktop pc in my home on a Shaw provided internet connection, the only device with a POP3 setup for the local download and archive. There is mention of possibly IPv6 connections being an issue, that IPv6 was subject to filtering. Windows 11 upgrade did in fact turn on IPv6 by default. I manually turned off IPv6 and it did not make a difference. I still had the Thunderbird error. In conclusion, these explanations may still apply but as of right now I cannot confirm them.

There was mention of Cloudfilter blocking of my IP if it did not have a reverse lookup. I used the mxtoolbox link to check the IP address assigned by the ISP and it indicates that it does have a reverse DNS but it also indicates that it is on blacklists: SORBS DUHL Spamhaus ZEN and that it might be on a Cloudfilter blacklist. I have never heard of this before. I don't quite understand. When at home, all my mobile devices are using my local ISP internet connection through my router wi-fi connection with the same IP assigned to my desktop PC and they are not being blocked. There is a suggestion that the blacklists are associated with unusual high email traffic coming from an IP address. I have surprisingly adopted many more current communication technologies and I would say that like the rest of the world, probably 95% is SMS texting. I am not a business and I only occasionally send emails when I need to send a detailed, verbose message.

I have made an observation similar to the Shaw customer reporting their problem. Shaw is one of the biggest ISP providers in Canada. But technical support is very limited in the email area. They don't really have an email tech support staff. When I couldn't decode the Thunderbird log to identify why their server is disconnecting, I tried to get their support. The standard response from them is, the mail service is not a supported service, it is a side benefit/promo of their internet service. The documentation/instructions they provide for setting up email clients is only a courtesy and if you have any problems, use their webmail, and pound sand for anything else. And the reason I think is because they have no access to the mail servers themselves. The service is provided by Cloudfilter and Shaw ISP is hands off. They really don't have a clue! This suggests that if the only way to resolve my issue is to get them to do something (eg get a certificate for their email server) that ain't gonna happen.

So I am left with two options. I know if I turn off the secure connection, I can receive POP3 email and send SMTP email. Another option would be to switch to an secure IMAP connection and see if I run into the same issues. I have avoided IMAP because in the email universe, IMAP meant I could not download and store/organize/archive all my email locally. I would be perfectly happy if all my devices had IMAP connections and were able to see all email in real time online, delete and send while having one device, my Windows desktop, download copies of the mail, delete, send and at the same time organize/archive in a local hdd folder, any email downloaded. (This option may be moot if IMAP is incoming and the problem is with the SMTP outgoing.)

Does Thunderbird allow me to say, create a 'Local Storage Folder' with subfolders for organizing/archiving different categories/subjects/senders, etc.., and the copies do not get deleted when the originals get deleted from the IMAP account?

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Chosen Solution

re : I used the mxtoolbox link to check the IP address assigned by the ISP and it indicates that it does have a reverse DNS but it also indicates that it is on blacklists: SORBS DUHL Spamhaus Zen

ZEN is the combination of all Spamhaus IP-based DNSBLs into one single powerful and comprehensive blocklist to make querying faster and simpler. It contains the SBL, SBLCSS, XBL and PBL blocklists.

As the info implies you may be on a blocklist then it is worth to try to get your IP address taken off the various spamhaus SBL, SBLCSS, XBL and PBL blocklists:

there is information at that website on how to go about removal.


If you currently have a POP account and you are thinking of removing it in order to create an imap account: Create folders in the 'Local Folders' mail account and get copis of emails moved from POP into Local Folders before removing the Pop account from via Account Settings.

re :Does Thunderbird allow me to say, create a 'Local Storage Folder' with subfolders for organizing/archiving different categories/subjects/senders, etc.., and the copies do not get deleted when the originals get deleted from the IMAP account?

Thunderbird has a default mail account called 'Local Folders'. You can create folders in that 'Local Folders' mail account. Emails copied from an imap folder into a 'Local Folders' mail account folder do not synchronise with server. They are stored on your computer.

You can create an imap account and set up to download/synchronise all subscribed folders. You can create folders in an imap account and they will get created on the server OR you can create folders in the webmail account and subscribe to see them. You can choose to downoad full copies of emails into the imap folders.

Once you have an imap account, you can use : Menu app icon > File > Offline > Download/sync now Select checkbox: 'Mail Messages' Select checkbox: 'Work Offline once download and/or synchronisation is complete'

the 'Select..' button offers you the opportunity to check all folders are selected for full copy download. Once all set up click on 'OK'

download.Sync occurs and then Thunderbird goes into Offline mode. Going into Offline mode means no connection to server, so when coping a lot of batches of emails from an imap folder into the 'Local Folders' folders, no folder is connecting to server, so less chance of something going wrong.

suggest you always use the right click on highlighted emails >'Copy to' option because if something goes wrong the original still exists. If you can read emails in the 'Local Folders' folders you know you have a good copy.

You can easilly go back to 'Online' mode by clicking on the Offline/Online icon located far left in bottom 'Status bar'

When you perform a backup of the 'Thunderbird' folder containing Profiles to an external drive, everything is backed up. Remember you must exit Thunderbird before performing a backup. Backup 'Thunderbird' folder is: C://Users/Username/Appdata/Roaming/Thunderbird

Info on imap, synchronisation etc links:

more options

Again you have introduced me to something new. I used your Spamhaus link to check the status of my IP address and discovered that it was on the Policy Blocklist (PBL). According to Spamhaus, broadband customers are typically included in this list and that it does not mean that the emails are automatically blocked by the ISP, because in fact, the ISP is in control of that listing. I switched my email account to IMAP and followed the information you provided on how to use Thunderbird to download/copy/organize etc. and it looks like Thunderbird will do exactly what I want it to do, to maintain a history of my IMAP email communication. Thunderbird is also compatible with my Zebnet MailShelf Pro archiving program, which I use as a tool to create an additional independent backup/archive/browser of email downloaded by Thunderbird. I did not expect the switch to IMAP to resolve my email send issue because it only drops the use of the POP3 server for incoming mail; the outgoing mail is still sent to the SMPT server and the existing SMPT server settings recommended by the ISP were not working.

Following some of the links that you and Matt provided, I ran across some related pieces of information that got me thinking. I noticed that when I was testing the Thunderbird SMPT server settings, each time I picked the TLS Connection Security of SSL/TLS, Thunderbird's default port was set to 465. I would overide this with the ISP recommended port 587 and if I selected STARTTLS, which the ISP specified only for Android devices, Thunderbird's default became 587. So I said to myself, what if Thunderbird's suggested connection security setting of STARTTLS for port 587 was more specific/accurate than the ISP recommendation for non-Android devices. I researched the difference between the TLS and STARTTLS connection security. I discovered that the more secure connection option is an immediate implicit TLS connection to port 465. I also learned that many ISPs provide a single port option so as to not confuse their customers with having to decide between multiple ports. So they provide the TLS port 587 option as a single option and the email client is expected to submit a normal non-TLS password login and then follow that up by request to switch to a TLS secure connection. This is not the most secure way of doing the connection setup because during the initial non-TLS login, a bad actor could pretend to be the SMTP server and intercept the login. But this is the approach that many email service providers have taken.

So I set the Thunderbird Connection Security to STARTLS, Authentication Method = Normal Password, and Port = 587, and, lo and behold, I was able to perform an outgoing email send. I would have preferred to establish an implicit SSL/TLS secure connection right from the word go, the login, but that is out of my control and Thunderbird's control. I accept this as a reasonable compromise and is a more secure connection than what I have been using for many years.

I would like to thank both you and Matt for your assistance. I have learned a lot this past week and you have provided may tools that I can use in the future. I hope that if others read this post, they recognize the effort you have gone to, to support me, a Thunderbird user, and in return, support you and the Thunderbird team.

Now. Off to make a donation.

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Good to hear you are able to send again.

re: Now. Off to make a donation.

thanks for your support. You can get a direct link to the 'Thunderbird' donation webpage via Thunderbird.

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