Thunderbird Community Forum

The past couple of months, sending emails has been difficult. I did all the troubleshooting, such as verifying the network settings, allowing a longer time for connecting, tweaking Avast settings, rebooted the Spectrum modem, etc. It doesn't seem to matter if the email is only text or if it contains graphics or attachments. I have 6 Roadrunner accounts in Thunderbird, and the problem is with all of them. I have automatic updates turned on. Sometimes it takes several tries to get the email sent. Thunderbird is sending some of the "not sent" emails to a local folder, which is hard to get them out of. What am I missing? tnx

dal mio account tizianomorselli@gmail.com sono scomparse le email inviate e ricevute dal 23/04/26 al 23/10/26. Non sono nel cestino non sono nello spam e non sono nell'archivio.

Emails sent and received between 26/04/23 and 26/10/23 have disappeared from my account, tizianomorselli@gmail.com. They are not in the trash, not in the spam folder, and not in the archive.

I need assistance with a persistent Microsoft 365 authentication problem in Thunderbird on Windows 11.

My business email is hosted through GoDaddy's Microsoft 365 service. Thunderbird repeatedly fails when attempting to send messages, displaying:

"Login to server smtp.office365.com with username [business email address] failed."

We have attempted to troubleshoot this problem on several occasions without achieving a reliable solution.

Previous troubleshooting has included checking SMTP settings, STARTTLS, OAuth2 authentication and investigating Microsoft Graph integration.

Our earlier investigation also indicated that SMTP AUTH may be disabled for the Microsoft 365 account.

The mailbox works through Microsoft Outlook, but having to remember to use Outlook separately creates a risk of missing time-sensitive business correspondence.

I would particularly appreciate assistance with the following:

1. Establishing a reliable, supported connection between Thunderbird and my GoDaddy-managed Microsoft 365 mailbox. 2. Determining whether Microsoft Graph integration can resolve this without enabling legacy SMTP authentication. 3. Identifying any known compatibility issues involving GoDaddy-managed Microsoft 365 accounts. 4. Providing specific diagnostic instructions so we can establish why authentication is failing rather than repeating unsuccessful configuration changes.

I can provide screenshots, Thunderbird version information and diagnostic logs with sensitive information removed.

I would be grateful for detailed technical guidance because repeated attempts to resolve this issue have been unsuccessful.

I cannot receive mail from my Outlook.com account in Thunderbird. This does not appear to be a Thunderbird configuration problem.

Thunderbird 159.0 on Windows. IMAP: outlook.office365.com, port 993, SSL/TLS, OAuth2, username = full address SMTP: smtp.office365.com, port 587, STARTTLS, OAuth2, username = full address

The Microsoft sign-in window completes successfully and an OAuth2 token is issued and stored. Using the same token: 1. SMTP AUTH XOAUTH2 succeeds: 235 2.7.0 Authentication successful 2. IMAP AUTHENTICATE XOAUTH2 fails: NO User is authenticated but not connected. 3. POP3 AUTH XOAUTH2 fails with an authentication/protocol error

I also reproduced the IMAP failure with a raw IMAP connection, outside Thunderbird. A brand-new Thunderbird profile still fails for this Outlook.com account; a Gmail account in the same profile works normally. Thunderbird is up to date.

Outlook on the web works. IMAP is enabled in Outlook.com settings (toggled off and back on). The same IMAP failure happens on two different networks.

I have already contacted official Outlook.com support. They said IMAP is outside their scope as long as Outlook.com works in the browser, and directed me to Feedback Hub.

Is there any Thunderbird-side workaround, or any known Outlook.com IMAP OAuth2 bind issue and recommended next step?

Hi,

For both servers imap.exmail.qq.com / imap.263.net, when I click on the email subject in the email list during downloading processes (many emails headers are being downloaded but email body downloading is not completed), the email is broken without any content (only header).

I go to the web email server and move the email to another folder and then move it back to inbox. Then I delete the same email in Thunderbird and donwload again the email again, it's completely downloaded with the email body.

I don't have any issue with eM client or Outlook for such issues. Any possible setting to solve this issue?

Thanks.

After years of mailing committee meeting notices, suddenly in the last 2 weeks they are being 'failed' because of being 'too many' recipients (only 20 btw) and am being told 'try later'?! Pierre

Hello Thunderbird Support Team,

I am experiencing serious email problems with Thunderbird on two Windows 11 computers.

I use Thunderbird for approximately 12–13 email accounts, mostly Gmail accounts, for my accounting work.

• • The main problem:**

Thunderbird receives incoming emails, but I cannot send messages from multiple accounts.

On the first computer, Thunderbird displays the following error:

"Sending of the message failed. The connection to the outgoing server (SMTP) smtp.gmail.com timed out."

On the second computer, Thunderbird repeatedly asks me to authenticate my Gmail accounts again. The authentication process does not seem to resolve the sending issue.

• • What I have already checked:**

- Thunderbird version: 153.6.0 ESR on the first computer. - SMTP server: smtp.gmail.com. - Port 465 with SSL/TLS and OAuth2. - Tested port 587 with STARTTLS – same problem. - Thunderbird successfully establishes a secure connection to smtp.gmail.com:465, but sending emails still fails. - Cookies, including third-party cookies, are enabled. - Tested Thunderbird Troubleshoot Mode. - Restarted Thunderbird and Windows. - The problem occurs on two different computers and different Wi-Fi networks. - Gmail accounts work through the web browser.

• • Additional information:**

The problems initially appeared when one Gmail account stopped synchronizing. I removed that account from Thunderbird, but its IMAP server configuration remained in the Thunderbird profile (prefs.js).

I subsequently experienced sending problems with other accounts.

I found Bugzilla report 2062925, which appears to describe similar problems involving multiple Gmail accounts and SMTP timeouts.

• • My questions:**

1. Is this a known issue in Thunderbird 153 ESR? 2. Could a malfunctioning Gmail account or an orphaned IMAP configuration interfere with SMTP sending from other accounts? 3. Is there an official fix or workaround that does not require deleting and reconfiguring all accounts? 4. Could Google OAuth2 authentication or Google Contacts synchronization be responsible?

I would appreciate your help. I rely on Thunderbird for my daily accounting work, and I cannot currently send emails reliably.

Thank you in advance.

Thunderbird

Configuration

• Windows 10 Desktop
• Multiple Email accounts managed by Thunderbird
• Functioning "normal" for multiple years

Problem

• One of the email accounts has been put together as almost a clearing account where all of my other emails are auto-forwarded from the email to the inbox of the account in question.

* Recently this account has stopped accepting emails either by auto transfer or by cutting and pasting emails into the inbox and also by cutting and pasting from a folder within that email account to the inbox.
   

Identified Issues

       When looking at the account settings, I noticed that the account in question with the input issue also, next to the account name, has a mustard-yellow-colored star that none of the other accounts have. I don't see anywhere in Help, Technical, or whatever any meaning for what that means. That's where I think the problem lies. 
   Potential Solutions
       As a workaround I have started forwarding emails from one email into The account in question as a clearing account this clearing account. That involves taking an account from Gmail (as an example) and forwarding it to a folder that specifically is for input from Gmail ... but then the filters don't always work because they're not going through the input box. 
       Do you have any suggestions or fixes that I should be aware of and try? 

	Thunderbird Version 	153.6.0esr   Build ID 	20261026222624

Since yesterday when I open Thunderbird to check my bigpond emails on my laptop I get a message that says "Enter your password for mail.bigpond.com" - I've never had to enter a password in all the many years I've been using Thunderbird on my lap top. I can get the emails on my phone and on Telstra webmail but I prefer Thunderbird. Also get a message that says "Mozilla Thunderbird login timed out" When I put in the password I use for Telstra webmail it says "Host contacted sending login information" but then I get another message Login to mail.bigpond.com with user name [redacted] @bigpond.net au failed Retry...

Not sure if this is connected to not getting emails on my phone for a week and going in to Telstra yesterday where they fixed that problem...

I have two accounts set up in Thunderbird using POP settings. I'm having trouble with email from one of the accounts being downloaded into both of the inboxes.

Any idea how to remedy this?

Thanks!

My two Optimum email accounts (POP3) stopped sending messages. See attached error message. They are still working on a different computer with the exact same settings and Thunderbird version (Windows 10 on both too). I also have Outlook and Gmail accounts all still sending fine. Sending from troubleshooting mode and clearing the startup cache didn't help. Any clues what I can try?

Mac OS 26.7.1.

There are 2 responses to IMAP command 103. IMAP command '104 IDLE' between the 2 responses. The first one is correct. The second one!!! is identical to the first one except it is prepended with the letter 'p'!!!. Always the letter 'p'. It looks like a programming error.

Note that the entry in prefs.js for this main account is broken since migration for Thunderbird 155.0.1 to 156. Every time I change some settings in the Identity section, 2 prefs.js entries are removed: mail.identity.id1.fullName and mail.identity.id1.useremail. This prevents me from sending emails from this account until I enter the proper values from the Prefs editor. I realize this is 2 problems but I think one may cause the other. Note that I have a second Yahoo! account that works perfectly well.

Thanks for any advice.

330626000.txt:

2026-10-24 16:23:22.455152 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:A:SendData: 93 ID ("name" "Thunderbird" "version" "158.0.1") 2026-10-24 16:23:22.946354 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:A:CreateNewLineFromSocket: * ID ("version" "1.1.26730" "host" "localyahoo.serving-api.mail-serving-jimap-prd.gcp.yahoo.cloud" "name" "Y!IMAP" "vendor" "Yahoo! Inc." "support-url" "http://help.yahoo.com/" "remote-host" "67.195.177.120" "via" "jimap400041.imap.mail.yahoo. yahoo.cloud|localyahoo.serving-api.mail-serving-jimap-prd.gcp.yahoo.cloud") ... 2026-10-24 16:25:51.321640 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:ProcessCurrentURL: entering 2026-10-24 16:25:51.321712 UTC - [Parent 23990: Main Thread]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:SetupSinkProxy: got m_imapMailFolderSink 2026-10-24 16:25:51.321793 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:ProcessCurrentURL:imap://XXXXXXXX.XXXXXX%40ymail.com@imap.mail.yahoo.com:993/select%3E/INBOX: = currentUrl

2026-10-24 16:25:51.323962 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:SendData: 102 noop 2026-10-24 16:25:51.866542 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:CreateNewLineFromSocket: 102 OK NOOP completed

2026-10-24 16:25:51.866628 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:SendData: 103 UID fetch 388684:* (FLAGS) 2026-10-24 16:25:52.088074 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:CreateNewLineFromSocket: * 9700 FETCH (FLAGS (\Seen $NotJunk) UID 388683) 2026-10-24 16:25:52.392757 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:CreateNewLineFromSocket: 103 OK UID FETCH completed <<<<============ 2026-10-24 16:25:52.426006 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:ImapThreadMainLoop: idlePending set

2026-10-24 16:25:54.431078 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:SendData: 104 IDLE 2026-10-24 16:25:54.544903 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:CreateNewLineFromSocket: + idling 2026-10-24 16:25:54.545022 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:HandleIdleResponses: idle mode async waiting

2026-10-24 16:28:20.264066 UTC - [Parent 23990: IMAP]: I/IMAP 330626000:imap.mail.yahoo.com:S-INBOX:CreateNewLineFromSocket: p103 OK UID FETCH completed <<<<============

p103 OK UID FETCH completed !!! (Server error or client error?)

I currently have spectrum service and have gone through this with them. Everything is fine on their end. TB is throwing this message when I try to send an email.

"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."

It all worked fine until last week.... Once this started, I changed all servers / ports etc to the settings Spectrum suggested to no avail.

Any ideas?

I sent email, email goes out from thuderbird but copy is not saved is "sent mails", its only for one receiver, for all other it works, why? before it work for this receiver too

A few days ago, when I opened Thunderbird, it began downloading all folders and emails from my server provider ( bringing the folders to date) I already removed the account and the database twice to see if it was a database issue, but it keeps refreshing all my folders and emails, which is a huge amount and takes a long time to complete. Any idea how to troubleshoot or fix this? Thanks