I-Thunderbird Community Forum

I can receive but not send messages, this has been going on for over a month now. I've tried several times to fix this but unable to correct it. The first error message prompted me to check password which I did. It worked for a few days, then it didn't. Checked with my IP to make sure I have the right port number and security settings: Port: 587, SSL/TLS. Started getting other error messages... this one is the latest: The message could not be sent because the connection to Outgoing server (SMTP) smtp.comcast.net was lost in the middle of the transaction. Try Again).

I'm on Macbook Air (Sierra 10.12.6). Using Thunderbird (115.18.0 (64-bit), says it's up to date. I've attached the last two messages and a snap shot of my smpt settings. My brain is fried from trying to figure this. I'm also wondering, if my OS software no longer supports this version. Any help would be greatly appreciated.

Hi I tried to google this but as you can guess that was a exercise in futility.

So I installed thunderbird via flatpac as suggested by the main website

I went to account add a account entered my email and password.

Clicked continue twice setup filled in the info and got a error saying

Authentication error.

Unable to log in at server. Probably wrong configuration, username or password.

now i know both are correct as i logged in vai firefox and checked both excepted.

pic below best i can do dam thing wont let me set window size so it got cropped hopefully gives info needed

so I tried to google the settings of incoming and outgoing 4 out of 5 pages i found where set as the pc has set it.

at a loss now guys no clue what to do any help would be appreciated.

ty in advance.

hello everybody thank you for your help i have a connection problem between thunderbird (ubuntu 26.04) and my email provider mail.fr. When i open thunderbird the following message appears "unable to connect to imap mail.fr".

But I have a second computer also under linux 26.04 which has no problem. The installation is the same, automatic.

So I don't understand why this connection is not made. I checked the passwords, the connection timeout, I redid the thunderbird installation, I recreated the email account mail.fr...

I don't understand. If anyone has an idea, a tip, I'm all for it. The problem does not come from mail.fr, because I access my emails on their site without any problem.

thank you in advance for your help jmb

Cannot send or receive email all of sudden in Thunderbird. When I the click the messages icon, nothing happens, and I get "Could not connect to server mail.twc.com; the connection was refused". When trying to send a m,message I get "Sending of the message failed. The message could not be sent because connecting to Outgoing server (SMTP) mail.twc.com failed. The server may be unavailable or is refusing SMTP connections. Please verify that your Outgoing server (SMTP) settings are correct and try again." No settings were changed and everything was fine when I put the computer to sleep. This happens on both a Win 7 and 11 machine Email is a Time Warner (now Spectrum) Road Runner account (twc.com). Spent an hour with Spectrum, and they say this is a third party (Thunderbird) issue. A friend has the same setup, and is having the same problems that started at the same time. Win 11 version 150.02 Win 7 115.18.0 (latest available for win 7)

Appreciate any help....

After system complete reinstallation Ubuntu 24.04 it is not possible to send mails with SMTP Server. Receiving messages is possible!! Two fault Messages happen, I've two SMTP servers: 1. No connection to SMTP possible 2. Server timeout

And yes, I've checked nearly everything what's to find in the internet, reinstallation, change and check settings and passwords, together with the specialist from my provider. Also my provider is not able to find a mistake. As I've found out in the net, there are sometimes problems to connect to SMTP, but no solution found. Is there some security in the UBUNTU system, which blocks the SMTP connection or is this a bug from Thunderbird? Thanks in advance Andreas

1. 1. Thunderbird connects to my IMAP/SMTP server but neither receives nor sends mail

I am having a problem with Thunderbird on Windows with a custom-domain email account hosted by Advika Web.

1. 1. 1. Account

Email address: `connect@synergyappstudio.com`

Mail hosting provider: Advika Web

The mailbox and password are confirmed to be valid because I can successfully log in to the provider's webmail using the same email address and password.

1. 1. 1. Server settings provided by the hosting provider

Incoming IMAP:

• Server: `mail.synergyappstudio.com`
• Port: `993`
• Connection security: SSL/TLS
• Authentication: Normal password
• Username: `connect@synergyappstudio.com`

Outgoing SMTP:

• Server: `mail.synergyappstudio.com`
• Port: `465`
• Connection security: SSL/TLS
• Authentication: Normal password
• Username: `connect@synergyappstudio.com`

1. 1. 1. What happens in Thunderbird

Thunderbird shows:

> Connected to mail.synergyappstudio.com

However, incoming messages are not downloaded and outgoing messages cannot be sent.

The SMTP error I received was:

> The connection to Outgoing server (SMTP) mail.synergyappstudio.com timed out.

1. 1. 1. Connectivity tests

I tested the server from Windows PowerShell.

Port 993:

`Test-NetConnection mail.synergyappstudio.com -Port 993`

Result:

> RemoteAddress: 103.69.196.146 > RemotePort: 993 > TcpTestSucceeded: True

Port 465:

`Test-NetConnection mail.synergyappstudio.com -Port 465`

Result:

> RemoteAddress: 103.69.196.146 > RemotePort: 465 > TcpTestSucceeded: True

Therefore, both TCP ports are reachable from my computer.

1. 1. 1. TLS tests

I also tested the actual TLS handshake rather than just TCP connectivity.

TLS 1.2 against IMAP 993 failed with:

> Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.

TLS 1.0 against IMAP 993 produced the same result:

> Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.

I also tested the TLS handshake against SMTP 465 and received the same "connection was forcibly closed by the remote host" result.

1. 1. 1. Comparison with Outlook

There is an important comparison:

The same mailbox **successfully connects and authenticates in Classic Outlook** using the same server and credentials.

However, I am using Microsoft Office Home & Student, so Classic Outlook is not available to me as a practical permanent solution for this business email account.

Microsoft's **New Outlook** also fails to add the account and displays:

> Sign in failed. Please try again in a few minutes. You may need an app password.

The mailbox does not use Microsoft 365 authentication. It is a conventional hosting-provider IMAP/SMTP mailbox.

1. 1. 1. Thunderbird troubleshooting already attempted

I have:

• Confirmed the password works through webmail.
• Confirmed the supplied IMAP/SMTP server names.
• Confirmed ports 993 and 465 are reachable.
• Confirmed SSL/TLS settings.
• Used Normal Password authentication.
• Used the full email address as the username.
• Tried Thunderbird with the supplied IMAP/SMTP settings.
• Reduced **Maximum number of server connections to cache** from the default 5 to 3 and then to 1. This did not resolve the problem.
• Restarted Thunderbird after changing the connection-cache setting.
• Tried Thunderbird's connection logging, but the generated log files remained 0 KB, so no useful log was produced.

1. 1. 1. Additional observation

Thunderbird displays "Connected to mail.synergyappstudio.com", but the account does not actually synchronize incoming mail.

The provider's webmail works normally, and Classic Outlook works with the same mailbox.

1. 1. 1. What I would like help determining

Could you please help determine whether this is:

1. A Thunderbird IMAP/SMTP compatibility issue with this particular mail server; 2. A TLS negotiation issue; 3. A Thunderbird configuration/profile issue; 4. A Windows/security-software interaction; or 5. Something specific to the mail server's IMAP/SMTP implementation?

In particular, I would like to understand why Thunderbird can establish the connection but cannot complete the IMAP/SMTP communication, while Classic Outlook works with the same server, ports and credentials.

I can provide Thunderbird version information, Troubleshooting Information, screenshots of the account configuration, or any additional diagnostic information you need.

thunderbird has stopped receiving e-mails from century link. Configurations worked for two years as pop3, now won't connect. Tried imap configuration, same issue. Changed password (CenturyLink has problems with some password characters), still will not connect. AI (co pilot) tells me it is an issue since CenturyLink made changes, but they blame the email app (tried with Samsung app, thunderbird, outlook, none will connect. Connection thru CenturyLink web page works fine.

Hello,

I recently upgraded to a new PC from Windows 10 to Windows 11. For some reason I can not open links in any emails, even if right clicking them. I have gone through all steps here: http://kb.mozillazine.org/Standard_diagnostic_-_Thunderbird but nothing has changed. I have disabled Win Defender completely and still no change.

Any idea what I am missing? I am at a loss at this point.

Thanks for any advice or direction.

All was well until about six months ago. When I try to connect to my provider TB won't connect. BUT. At other times it will connect then every few minutes will try to connect again - then again .... I get this message "Connection to the server mail.comcast.net timed out". Then I get this message each time it fails "Login to server mail.comcast.net with username 170834000 failed". It keeps asking me to input my password even though everything is working appropriately. Then at other times it says it doesn't connect but it has connected and it still continues to ask me for a password.

I have uninstalled TB and reinstalled it thinking that would fix it - it didn't. I have changed my password - again to no avail. I let TB choose where to put things and configure each item appropriately. I don't try to get in the way of what works.

Comcast is apparently getting out of the email business and asking everyone to move over to their chosen substitute (Yahoo.mail) and I have not chosen to migrate at this point. Maybe that's the problem. This is the message I get each time I log into Comcast.net:

"A better email experience is now available for you

You're invited to upgrade your email account to Yahoo Mail, so you can enjoy a more user-friendly experience. Your email address, messages, folders, and contacts will not change.

With Yahoo Mail, you'll enjoy enhanced security, a built-in calendar that's easy to use, AI-powered inbox organization, and a top-rated mobile app for easy access on the go."

I am not aware of any changes in the settings from before when it was working well and now when it seems to be erratic.

I am not terribly computer savvy, but I'm usually able to trouble shoot and fix the issues that confront me. This time I'm out of my league! I need help.

Thank you for helping me.

Sometime ago, Thunderbird stopped being able to connect with my GMail and Hotmail email accounts. I guess this had something to do with the change to OAuth authentication. I then switched over to Yahoo accounts which worked perfectly until last night when I installed the latest update, i.e. 153.0.1esr (Meadow). Now, I cannot connect with ANY account whatsoever. Thunderbird just stopped working in my two Windows 10 laptops and it does not seem to work on the Windows 11, either, although I have only tried Gmail accounts on that one (without the update), as I cannot possibly be left without an email handler.

If I try to download my emails, I get a screen that tells me that I should “Turn-off ad blockers“ and “Enable JavaScript“ in my browser, but I have tried several (4) browsers as default with the same result. I don’t have either ad blockers or cookie restrictions in any one of them and JavaScript is enabled in all (it is now by default).

I have downloaded and installed “eM Client” and it works *perfectly*. However, I would loathe to have to abandon Thunderbird and get used to an entirely new program, but which is what I will have to do if this thing is not resolved ASAP.

As mentioned, I think there has to do with the OAuth authentication system.

I have even tried ChatGPT, without success!

And there is no way to revert to the previous version !!!!!

Please do something NOW, or it is, regrettably, goodbye Thunderbird!

thunderbird is not able to access mail.twc.com for 2 days now. Spectrum webmail didn't work yesterday, but is now functional. Thunderbird may need a fix to deal with whatever changes Spectrum made to its mail server,

Was working OK. Now, "No Apps Available" appears when I try to connect to the Yahoo mail server. The "Find more in Software" button causes the "Failed to start software" message to appear. The reinstall is from the App Center.

It also opens the following link on the Firefox browser which displays a blank page. https://api.login.yahoo.com/oauth2/request_auth?response_type=code&client_id=dj0yJmk9WVZUaWRNUUZSQTBNJmQ9WVdrOVNqbHJUMGhtTkU4bWNHbzlNQT09JnM9Y29uc3VtZXJzZWNyZXQmc3Y9MCZ4PTgz&scope=mail-w+ycal-w+sdct-w&state=AUCYywsENF9wWMx1nhJAefu3yJtqIlLxOCP9laluGgA&code_challenge_method=S256&code_challenge=BhhyhkNZvKm5SUrRFTxgmp3HR7vX26vggsjMoThl4wk&login_hint=randylh%40cox.net&redirect_uri=net.thunderbird%3A%2F%2Foauth%2Fyahoo

Everything has been fine for several years but this morning I now get error: TB could not connect to server mail.twc.com, the connection was refused. Spectrum says everything is good on their end. What do I have to do to "fix" Thunderbird? I can't send or receive any emails from 5 accounts with Spectrum and the emails are there when I log in at WebmailSpectrum.net..

The issue has been "An error occurred connecting to mail.mediacombb.net:993." on the server page, where you can "test connection to server" in Account > Server Settings > Security Settings. I get the same error message for each four different accounts. I have no problems with the other two different accounts not associated with Mediacom (MC). I contacted MC and they said my settings were correct and to contact TB. I have read several posts with no real solutions except that was resolved through an update. I plan to switch to a different Linux distro later. I am currently using Big Linux Manjaro with the latest update. Note that I had no problems with TB until last month. I do not do the uninstall/reinstall apps unless it will resolve my issues as a last resort. Second, sometimes I receive MC e-mails and did not run the "test connection to server," then until today while troubleshooting for several hours. I was trying to send out an e-mail, which I had no problems last week. I already went to Account > Server Settings > Advanced and changed the "Maximum number of server connections to cache" from 5 down to 1 with no luck.

  The e-mail server settings are:

imap.mediacombb.net 993 SSL/TLS Normal Password and smtp.mediacombb.net 587 STARTTLS Normal Password They have not been changed since I switched from windows 10 to Zorin 18 to currently Big Linux Manjaro. I attempted to locate a method to check if the server settings were correct via Terminal. M$ Outlook has a test page that you can send to yourself or another e-mail account. Last, MC tech informed me that M$ Outlook is more friendly than TB. I know that I have used M$ Outlook for years and rarely had any connection issues unlike TB. Unlike Evolution, which was my first after M$ Outlook, TB is much better and easier than Evolution. Thank you in advance for your time and advice.

I still use Thunderbird on an old desktop and for the past month or more, I've discovered with some sort of communication error or the direct pop-up that I cannot login to server and it asked me to 'retry'/'Enter New Password"/"Cancel" and it's beyond frustrating. I'm on the verge of just uninstalling this for my emails and use another platform. Before so, since I've been using TBird for a long time, I figured I'd consult some experts here to guide me how to navigate this annoyance. ANY suggestions would be appreciated. Thank you.

Please see attached image of the problem.

I have tried looking on Google for ideas but have not found anything on this or how to fix. Hope someone can please help would be amazing!

Google -

400. That's an error

The server cannot process the request because it is malformed. It should be retied. That's all we know.

Has anyone had issues with Thunderbird sending and receiving email? I can only send or receive when my wifi is turned off on my phone.

I've tried deleting the app and resetting all network settings on my Android phone but still no joy.

Salve, Rispondo alle precedenti in merito ai problemi di connessione e quindi di configurazione di un account gmail sul vs client. Dalle vs risposte pare non ci sia soluzione. Se è così è un peccato dopo anni di ottimo funzionamento, sarò costretto a cambiare client.

Hello, from time to time my Thunderbird on my desktop PC running windows 10 doesn't receive emails, while they arrived on my I Phone 8. Checked my Telstra web mail, all emails are there so what is stopping getting to my desktop PC? I thought the Thunderbird receives emails than synchronize with my I Phone? As you can see from my 2 images the Telstra is up to today as is my I phone But Thunderbird is 3 days beyond. Tomorrow it may back to normal or the next day? I am returning to this message the next day 16/06/2026 1 more message on my I Phone, still nothing on my Thunderbird.

An other problem I get with Thunderbird is that a message appears on the right bottom of my screen: "Mozilla Thunderbird Connection to server mail.bigpond.com timed out" and/or "failed to connect to mail server imap.telstra.com" If I try to send an email after the above notifications, I get the "Connection Refused". I know than to just walk away. I am using Starlink as Telstra here doesn't work as I am on the fringes of Melbourne in a BLACK HOLE. Any help will be gratefully received. Thank you for reading this. Regards Ilio Pieroni