Thunderbird Community Forum

Hello,

My internet provider is RCN. For the past couple of months, I’ve occasionally been getting the message, “Connection to server imap.rcn.com timed out.” As a result, I’m unable to receive emails via Thunderbird.

All my settings are correct. Usually, the problem resolves itself within 24 hours, but sometimes, like this time, it lasts longer.

Any suggestions? Best, Magda

First, thank you for your work with Thunderbird. I am on Thunderbird portable esr update channel. I connect to work email outlook. How do I manage a transition given that Microsoft will stop ews on October 1? Is there a new version of Thurderbird that will be released through the esr update channel to allow connectivity to Outlook? With thanks.

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.

There's a box with 5 choices that comes up when I open TB email. The bottom one is about integration. Not sure what to do with any of them. I'm using a laptop for emailing

Thunderbird has stopped receiving or sending email. I just tried to send a message and received the following error message: "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.gmail.com timed out. Try again." This has been a problem for several days. Potentially since the last update. This a Windows 11 machine. Google server. Thunderbird v.154.0 (up to date) Please help. Thank you.

This only recently started happening. This has been tested on 3 different computers. Windows 10 Pro on all three.

With VPN on: Bluemail works fine.

Thunderbird can connect and download messages, but when I try to send a message, it gives an error.

With VPN off:

Bluemail and Thunderbird both work fine.

I am using on Mozilla VPN on my Linux computer. Thunderbird is my email program. My ISP is Spectrum. I have a very old rr.com account. When I instruct Thunderbird to "get mail", it gives me a pop-up "Thunderbird connection to server mail.twc.com was reset". The only way to stop this is to disconnect my vpn.

Is there a way to stop this behavior? I would prefer to leave the vpn on at all times.

BTW, I am in the U.S. and select a location in the U.S. for the vpn.

Thanks.

Been longtime user of Thunderbird. On 8/6/2026, Thunderbird refused to connect with the email service provided by DirectLink, Canby Telephone Association, Canby, OR. Have been working with Live Chat to restore connection. Have removed and reloaded Thunderbird. When I put in Security Setting under Connection security (SSL/TSL) and then test the setting, I get an error occurred connecting to mail.canby.com:993. DirectLink techs say they have done everything in their power to check their connection with Zimbra mailbox. Then they say, contact Thunderbird. I have been on Live Chat several times and they have checked my settings and my ipv4 settings. Tell me what I can do to get the email system to operate as it should. Clyde Hockman 503-592-4490

Thunderbird e-mail does not connect to the server. It times out. Internet connection is good as verified with service provider. I have exited from the email and tried to connect again. Still no connection.

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.

There seems to be an incompatibility between Thunderbird and Comcast. I stopped being able to send emails from 2 different computers a few days ago. Comcast has gone to IMAP and I had POP3. When I deleted my TB email accounts and tried to re open them as IMAP, the connection was refused by the server. I've spent hours on the phone with Comcast, but there was no solution. I've switched to Outlook and it works fine as IMAP. I would like to use Thunderbird again. I have 10 years of important emails stored in the local folders so do not want to lose them. I think this is a problem between Thunderbird and Comcast, but no one owns the problem, except me. Is there a solution? Thanks, Larry Kapinos

I'm getting "Thunderbird can't connect to the server" message, so I can't download messages. However, a message or two will finally download 1-2 hours later.

Same problem on 2 laptops, both running Windows 11. But I know my emails are coming in as I can view them via Spectrum webmail. So the problem isn't the Spectrum servers.

I've logged out and back into Thunderbird, and have re-booted my laptops. No luck. What to do?

Also, is there a place to report problems directly to Thunderbird?

Thanks for any help.

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.

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.