Test the possible effect of antivirus (what is it?) or other startup apps by running Windows in safe mode.

Had already done these things, even though this pc has the same apps and the same AV as the other 12 PCs in the office on which Thunderbird works just fine. As I said, this PC's Thunderbird worked for YEARS until suddenly it stopped.

EMClient works. Outlook works. MS Mail works. Webmail works. Thunderbird does NOT work. Someone has some ideas. Please. This customer likes Thunderbird, and does NOT like the others. Can someone please help? I have even re-installed an older version with no change in behavior!!

I have invested over 10 hands-on hours in this issue, more time than it takes to solve most server or network issues. I have removed AV and firewall with no effect. I have restarted in safe mode with no effect. I have uninstalled, removed directories, cleaned registry entries rebooted and re-installed with no effect. I have even gone through the above again in installing an older release with no effect.

Until/unless someone out there has a suggestion I have not tried, I see no point to my further investing time in this issue.

As do all the other members of the customer service staff at this client location, this user has 4 email accounts which all receive mail but fail to send ONLY ON THIS PARTICULAR PC. This morning I am advising the customer to purchase a copy of the paid EM Client for this user, which I will install. I currently see no alternative. I am greatly disappointed that no one in the community does either, and this will force me to re-evaluate my recommendations to use Thunderbird going forward at the businesses that I support.

That thunderbird has no regular support channel makes its use in a business environment problematic at best. Please inform me if this situation changes.

Regards. And good luck.

We do not know very much about your situation other than one computer will not send for an unknown reason and that you have performed a completely clean install.

What Thunderbird version are you using on the problem computer and is the same version being used on all computers?

Did you get the download from the official webpage?

• https://www.thunderbird.net/en-US/thunderbird/all/

What OS are you using on the problem computer and is the same OS being used on all computers?

What Anti-Virus are you using? ESET ? Is it the same AV as used on all computers ? Is Firewall blocking outgoing port? In Firewall, Thunderbird needs to be an allowed program.

What server are you using eg: gmail account etc What are the known SMTP settings you are using that work on other computers ?

Is Thunderbird installed into the default location? eg: Windows 10

• C:\Program Files (x86)\Mozilla Thunderbird

Are profiles stored in the default location? eg: Windows 10

• C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>

When you attempt to send an email what happens ? Do you get an error message ? If yes, what does it say word for word ? An image showing this would be helpful.

Did this 'not sending' occur immediately after an update? Thunderbird update or computer update etc?

Menu app icon > Options > General Under 'Network & Disk Space' section Connection...click on 'Settings' What are the current settings? - post an image Are those settings exactly the same as used on other computers ?

Is the computer using a wired/ethernet or wireless connection ? If wireless then perform a test with ethernet cable.

Have you performed this test: On computer which has problem Exit Thunderbird Access the 'profile name' folder and copy all the contents of that folder - not the folder itself. paste into a suitable device to move between computers.

On a computer where thunderbird is working ok for that user. Create a new profile. Exit Thunderbird Access new profile and delete all contents - then paste in all copied contents of the copied profile.

Start thunderbird and select to run that new profile: Help > Troubleshooting information Under 'Application Basics' section - click on 'about:profiles' locate new profile and click on 'Launch profile' which has all the contents of same profile on problem computer.. Can you send an email?

If yes, then the issue is with the computer and not the profile.

I will attempt to be polite, but I am annoyed at some of these questions. I apologize in advance if the following looks like a rant. I am extremely frustrated with an email client that should work but doesn't, and the scarcity of viable remediation suggestions.

Did you get the download from the official webpage? < duh. where else would I get it ? China maybe. Insulting question. I started with computers in 1967 and learned a long time ago to do things right and get software from reputable sources.

What OS are you using on the problem computer and is the same OS being used on all computers? <<=this PC is win7 pro. The other PCs are an even mix of win7pro and win10 pro. Also the AV is the same everywhere. Also turning off the AV and the firewall made no difference. Those were the first things I did!!!!

What are the known SMTP settings you are using that work on other computers ?<<==ssl/tls with normal password on port 465

Is Thunderbird installed into the default location? <<== no. I installed it on the Space station. DUH. another insulting question. You have the record for these. I learned a very long time ago to use the defaults when installing software. Everything is vanilla including the profile location.

I have already compared settings to other working PCs and will attest to no differences. I have also opened the config editor on this PC and compared the settings to other PCs and found no differences. AND NO, I will absolutely NOT run the risk of doing a FUBAR on a working PC to test this one. I have already wiped out all folders including the profile folder and the registry entries and did a clean install of both the current release (FROM THUNDERBIRD.NET) AND VERSION 60.X ALSO DOWNLOADED FROM THE OFFICIAL SITE LONG AGO AND STORED IN MY ARCHIVES) AND THIS MADE NO DIFFERENCE!!!

The network environment is a wired network with a Cisco-Meraki MX internet appliance and Cisco-Meraki 48 port managed switch. The network is mature, includes a VMware host with 2 windows server guests and 3 Linux guests. Everything works, except Thunderbird on this single device. My goal is to fix this single device without breaking anything else that currently works. I now have EMclient installed on this PC and it works with settings imported from thunderbird.

You really do know how to insult those who have given their free time to try to help in a voluntary capacity. Well, here is a heads up, nobody knows anything until you provide information.

You should not be annoyed by any question nor rude when someone asks a question. It really does not do you any favours.

Obviously, the first thing anyone needs to know is the setup and situation. You should not assume that others automatically have a working knowledge of all your various PC's, network, etc etc. You have been in the IT industry for long enough to know this.

None of my questions were irrelevant. Plenty of people do not install in the default location and plenty of people do not necessarilly run profiles in the default location and I've known situations where not all computers were running the same AV nor same OS. You see, I do not presume anything.

It is so simple to test a profile - (that is only the contents of that profile you would copy, not the profile name folder itself) - is working on another working computer of same OS, so you can rule out any issue with a profile. That tells you there is nothing wrong with the profile, so removing it and recreating it would be a futile operation. It saves you a lot of time and effort looking in the wrong direction.

You say the problem is specifically with sending, I did ask you to provide specific information about this, but you forgot to include the information. Clearly, if there is an issue with sending then this information is important. When you attempt to send an email what happens ? Do you get an error message ? If yes, what does it say word for word ? An image showing this would be helpful.

Did this 'not sending' occur immediately after any update? Thunderbird update or computer update or AV update?

Saying same AV is on all computers is useful, but it does not inform us which AV you are talking about. As you may be aware, simply switching off an installed AV is not sufficient as the default on computer may operate instead. When you say I tried in 'Safe Mode', I presume on this occasion you were talking about 'Thunderbird safe Mode'.

Did you restart the Win7 computer in 'Safe mode with Networking' and then start Thunderbird as normal to test sending?

Is IPv6 enabled? Are you using AV that auto disables IPv6, so maybe an update occured and it reset to default?

I apologize for offending. I am extremely frustrated by this problem. As you will see from the screen shot of the error, it tells us nothing at all except what we already know. Namely the sending failed. I have reinstalled clean I have tried different versions, all from the official source I have restarted TB in safe mode I have restarted the PC in safe mode with networking IPv6 is NOT installed on this PC - never has been. I have disabled the windows firewall I have REMOVED the antivirus nothing has made a difference! TB continues to work perfectly on all other PCs at this site. It worked perfectly on this one too until suddenly it didn't. There is no correlation with TB update. This PC has not gotten any windows updates in a long time, so there is no implication of causality there either.

I am stumped. And tired.

Are they all using the same Thunderbird version? Thunderbird 78 removed support for SSL and TLS prior to version 1.2 so the Thunderbird version between what works and what does not is important. It is also likely that emcleint ( I did not like it at all) and the microsoft products have not implemented the industry wide removal of these old versions as Thunderbird is more aligned to the browsers and gets to these sort of changes by default much before the paid clients.

What has surprised me are the number of mail servers out there with 20 year old SSL/TLS versions but not the newer ones.

Beyond that I can really only suggest you log the SMTP traffic https://wiki.mozilla.org/MailNews:Logging#Windows at least that way we can get to the actual commands that are causing issues. Or determine that nothing is coming back from the server and it is probably a firewall or DNS issue.

I am about ready to throw in the towel.

FIrst, if this was a firewall or DNS issue, no other client would work either because they still have to resolve the same smtp server and use the same protocol/port.

I have also used config editor to change the minimum tls to 1 and the fallback to 1 for testing. Restarted TB, still gave the same dialog box about not sending. Also restarted the PC, verified the settings in config editor, and they were still as I had set them. Still unable to send. Yet, on this same PC EM Client works, Mailbird works and even Outlook (AKA outhouse) works.

Set up smtp logging as per your suggestion. TB does access the file specified in the bat file because the file is locked when TB is running. On closing TB, the file is empty.

Perhaps there is some evil spirit or troll preventing the send. In any case I cannot think of any other place to look.

Just to recap...you did the following: Exit Thunderbird. Create the batch file and put on desktop. Double click on batch file opening cmd and starts Thunderbird. Select account to test sending Click on 'Write' create email and click on 'Send' A file is created on the desktop called 'smtp.log' When you exit Thunderbird, the cmd window also closes.

Open the 'smtp.log' file using eg: Notepad When you say "On closing TB, the file is empty." are you saying the 'smtp.log' file that was created is empty ?

On versions with User Account Control such as Windows 7, the batch file must be run with administrator privileges. So did you run the batch file by this method: Windows

Create a batch file by copying the lines below and paste them into the notepad application, and save the file as "create_imap_log.bat". Variables must not contain quotation marks.

set MOZ_LOG=IMAP:5,timestamp set MOZ_LOG_FILE=%USERPROFILE%\Desktop\smtp.log "%ProgramFiles(x86)%\Mozilla Thunderbird\thunderbird.exe"

Right click on the batch file and select "Run as administrator".

This should create and populate the smtp.log file when you send an email. Then copy and paste the contents of that 'smtp.log' file into forum so Matt and others can check contents to see if it offers some insight into what is going on.

Hello there bill188. We have read your message. We try to help you.

did you get a pop up window with an entry for example : Smtp error code 111?or other messages,ISP is blocking port?

Thunderbird cannot establish a normal connection for out going mail some reasons? https://support.mozilla.org/en-US/kb/cannot-receive-messages https://support.mozilla.org/en-US/kb/cannot-send-messages

copy and paste the contents please of that 'smtp.log' file into forum so Matt and others can check contents to see if it offers some insight into what is going on.

Port 578 to 993. Do not use port 25 just use 2525. Use antivirus and firewall software for spam traffic.

try to send a message to a smaller email box unknown not to the largest email boxes out there like gmail outlook etcetra.

See if this email gets there.

such mailboxes sometimes bounce back messages but also with impersonal messages such as delay and also specified messages that the user is not allowed for use for certain reasons such as identification.

https://tools.appriver.com/OpenRelay.aspx (Scannedwithvirustotal)

Greetings Firefox volunteer.

Thanks to all who have tried to help. I appreciate the attempts. But now I must move on. As an MSP that supports many businesses and many users, I do not have the luxury of spending endless hours chasing a problem which on its face does not seem logical. And I have to do what my customer tells me to do. They have said they can not wait any longer for this user to be able to send mail. They need it to work NOW.

If the cause was a large mailbox or busy server, sending to another local user with only a few messages stored would work. It does not. (BTW, their company mail is hosted on a Linux VPS, and they are the only domain hosted on that VPS. They have had this VPS for a long time.)

If it was caused by a firewall (which blocks specific ports) EM Client would not work, nor would mailbird or outlook. But they all DO work.

If it was the malware protection, none of the other 12 or so PCs at the same site that have the same malware protection ( and the same firewall) would not work either. But Thunderbird works fine on all of them.

Frankly, my customer is out of time.

The customer site having this problem has engaged an official trial of EM Client for this user. If it passes muster, they have decided to purchase the commercial version of EM Client for all of their users at all three of their locations. Meanwhile, if I can get time on the wayward PC to try again to get a log, I will get the log and post it because I would really like to know what is kicking me in the butt.

Thanks again. Best regards.