Thunderbird Community Forum

I receive email fine. The website email works fine. I cannot send email via thunderbird and have not changed my settings which worked for years. my smtp account. I have rebooted my Windows 10 pc numerous times. What can do this? How can I fix this>

I suspect there is no fix and I (possibly) can restore from backups, but I would sure like to know what the issue is.

I tried retrieving an e-mail from the "folder" where I kept e-mails from 2023. The "index" one sees displayed for the folder had e-mails from Jan-Mar of 2023, but Thunderbird froze when I tried to open any of them. I tried the repair function (which I imagine is meant to rebuild the .msf file), but after than the index contained nothing from Jan-Mar. I opened both the .msf file and the no-extension file in Notepad, but I see nothing from those months.

Any clues/help would be appreciated.

Certificate errors have been an ongoing, several-times-a-day frustration for me and other users, with different ISPs, since approximately June 25. Is anyone working on this bug? Because it clearly is a bug: Not only I but several other users have reported that Thunderbird worked fine until that date, then stopped working fine. What changed, and can it be put back the way it was, or can we receive some explicit instructions on how to fix it for ourselves? It's making Thunderbird borderline unusable. Every time I try to send a message, I have to confirm a security exception, then send it again. Several times a day, when I try to fetch messages, I have to confirm security exceptions. The confirmations never seem to stick. This is some BS.

Sometime in the past year or two, ONE of my four accounts started starring (putting the yellow star) on ALL emails I sent from that account.

This is not happening in the other accounts, including an account from the same university email system. If I send an email from the affected account (cischair) it is starred when viewed in cischair but not in the other account I sent it to (suthers). If I send an email from the other account, suthers, to cischair, it is not started in either account but my reply from cischair to suthers will be starred, again only when viewed in cischair, not in suthers.

It's very annoying to have to uncheck the stars on everything I send, and makes them useless.

Of course, I have looked in Account Settings for something that turns this on and off, and have not found anything.

Could you tell me where this might be set, or perhaps inadvertently by some keystroke combination (the bane of usability)?

Thanks - Dan

In transitioning from a Windows 10 Laptop to a new Windows 11 laptop, Thunderbird reports that "Thunderbird profile cannot be loaded. It may be missing or inaccessible" I've copied three times an 11gb Profile from the W10 to the W11 laptop using a micro SD USB transfer, which seems to be successful, and the file names are identical. The copy is directly from the Explorer location under User, AppData, etc. and conforms to instructions from Thunderbird.

Although Thunderbird runs fine with multiple email accounts In the Windows 10 laptop, when I clear Cache and restart Thunderbird, I get a message: "file link provider for WebDAV Account not properly configured". I don't know what that means. Don't know if this is causing the Profile problem.

Please help if you can.

Thanks, Gary Rubin garyrubin00@gmail.com

An extremely irritating bug in Thunderbird. Don't even remember how long it has been doing this; when I am typing a message, if I so much as switch away from the Thunderbird window (to look something up for example), when I come back to the window it will switch the font size to 1-2 points smaller than what it had been doing before. I have not selected any formatting settings, and had been typing in it's default type size. Merely switching out of the window should not perform a type size change.

I have ever had to just highlight the entire message (if TB has completely fubarred the font), delete it from TB, paste it into a plain-text editor to remove all formatting, and then paste it back in.

I am able to style tasks that are either completed/overdue/inprogress in userChrome.css . But so far I have not found a way to style canceled tasks.

Can someone help me ?

My Thunderbird is IMAP'ed to my generic usa.net email server. It downloads everything to Thunderbird serving as backup only. I have set that local delete does not delete on the server.

It has now amassed ~200.000 emails in the active Thunderbird Inbox. (No, I don't want to delete any !:o) I want to move the ~200.000 emails to a local folder not affecting the ongoing download sync from usa.net. The local folder is to be offline.

How do I bulk move the ~200.000 emails in the active Thunderbird Inbox to a local Thunderbird folder? - not deleting anything locally or on the server - keeping the sync download from the usa.net server running onwards into the now purged Inbox - not having the sync re-download from the server (defeats my intended purpose #:o)

Microsoft Outlook Client emails are legally valid in a court of law, but Thunderbird emails are not. Can we start taking baby steps towards making Thunderbird emails a little more viable in legal applications?

While I do not understand these things in the depth required, can we start taking baby steps towards achieving legal validity of emails downloaded from Thunderbird?

I am presenting below a conversation that I had with chat GPT regarding this matter for the help of anyone who wishes to take this up.

Chat GPT:

QUESTION 1: 1. As per my limited knowledge, Outlook client emails are legally valid because the header cannot be edited. This however, is not true of Thunderbird emails. Do I understand correctly? 2. What are the challenges in making Thunderbird header not user editable, so that Thunderbird emails also have the same benefit?

Chat GPT: Your question touches on email authenticity and legal validity—especially in regulated or evidence-sensitive contexts. Let's break it down:

Is it true that Outlook headers are immutable and Thunderbird’s are not?

Partially True — but needs clarification.

Email headers in both Outlook and Thunderbird

Can be viewed by recipients, but cannot be edited after the email has been sent. Only during composition can certain headers (like `From`, `Reply-To`) be changed, depending on the setup.

What you cannot change post-sending:

After an email is sent (from any client), the core SMTP headers (`Date`, `From`, `Message-ID`, etc.) are locked. These are generated by the sending server and cryptographically traceable via server logs or DKIM.

Outlook’s extra layer:

Outlook integrates closely with Microsoft Exchange, which stores server-side logs, message tracking, and non-editable audit trails (e.g., via journaling). That’s what gives Outlook/Exchange emails more evidentiary credibility, not just the client itself. In contrast, Thunderbird usually connects via standard IMAP/SMTP, without server-side logging, unless used with a corporate mail server like Postfix + Dovecot + journaling.

In Summary: Table Feature Outlook (w/ Exchange) Thunderbird Headers editable during composition Yes (some fields) Yes (same) Headers editable after sending No No Built-in server-side logging Yes (Exchange) No (unless configured) Strong evidentiary trail Common in enterprise Requires external setup

What are the challenges in making Thunderbird headers non-editable during composition?

The challenge lies not in technical impossibility, but in the design philosophy of Thunderbird:

a. Open Source & User Control

Thunderbird is open source, so users can customize or even extend the client to manipulate headers (via extensions or config changes). This is powerful for advanced users, but not ideal in regulated or high-trust environments.

b. Lack of Server-Side Enforcement

Thunderbird relies on whatever SMTP/IMAP servers it connects to. Unless the server enforces policies (like DKIM signing, DMARC, or header filtering), client settings are only soft limits.

c. Missing Native Audit Features

Outlook/Exchange logs metadata like when a message was sent, delivered, read, etc. Thunderbird lacks that unless paired with enterprise-grade backends. How Could Thunderbird Improve Legal Trustworthiness?

1. Header Locking During Composition

  	Disable or grey out fields like `From`, `Date`, `Message-ID`.
  	Possible via extension, but not enforced by default.

2. Enforced Server-Side Signing (e.g., DKIM)

  	Ensure outgoing mail is cryptographically signed to verify integrity.
  	Requires a properly configured mail server, not just Thunderbird.

3. Journaling or BCC Archiving

  	Auto-BCC all sent mail to a tamper-proof archival system.
  	Thunderbird can do this via rules or server configuration.

4. Extension or Mode for “Forensic Compliance”

  	Custom Thunderbird modes that restrict editing headers, disable extensions, log actions, etc.

Final Thoughts

You're correct in understanding that Thunderbird offers less baked-in legal reliability than Outlook + Exchange. But this isn’t due to insecure design—rather, it's due to Thunderbird’s flexibility and lack of tight server integration. Thunderbird can be made trustworthy with the right server configuration (DKIM, archiving) and possibly some custom add-ons.

If you’re looking to build or propose a “forensic-grade” Thunderbird environment, I can help design one with proper technical constraints and audit trails. Let me know!

QUESTION 2: My legal Counsel has told me that emails downloaded from the Gmail server into the outlook client are legally valid. So even without Microsoft Exchange and all the other server side logging, Outlook emails are legally viable. Chat GPT

Yes — your legal counsel is broadly correct, and here’s the nuanced explanation:

Emails Downloaded via Outlook (from Gmail) Can Be Legally Valid

Even without Microsoft Exchange, emails downloaded into Outlook (say via IMAP or POP from Gmail) can still be legally viable evidence, because:

1. Outlook stores email in a tamper-evident format

Outlook saves emails in `.pst` or `.ost` files. These files have a structured, proprietary binary format that is hard to tamper with without detection. Courts often accept these files (with chain of custody) as original records.

2. Outlook preserves server headers

Even when connected to Gmail, Outlook does not modify or fake headers. It shows server-signed headers (like `Message-ID`, `Date`, etc.) exactly as received. These headers can be verified independently against:

Gmail’s “Show Original” → raw headers DKIM/DMARC authentication

3. Integrity from Gmail itself

Gmail assigns unique `Message-ID`s and signs outgoing mail with DKIM. DKIM proves the message has not been tampered with since it left Google’s servers. So even if Outlook is the client, the source of trust is Gmail + DKIM, not just the software.

In Legal Contexts

4. What courts typically require is:

 A copy of the original message as received (headers intact)
 Some form of chain of custody (who had access, how was it stored)
 Optionally, confirmation from the mail server logs (if challenged)
 Outlook is often used in corporate/legal environments because:

It does not let users easily forge full headers The data format is harder to manipulate Legal teams and forensic experts are familiar with `.pst` files

So even without Exchange, emails received and stored in Outlook are trusted, provided:

The full headers are intact The `.pst` or `.ost` file has not been tampered with

5. How This Differs from Thunderbird

Thunderbird also preserves headers and stores messages locally — but: Table: Aspect Outlook Thunderbird Storage format `.pst`/`.ost` (proprietary) `.mbox` or plain text Header immutability Enforced by format Editable via text file (with effort) Forensic familiarity High (in legal circles) Moderate Tamper-evidence Strong (binary format) Weak (editable with text editors)

So Thunderbird messages can technically be altered more easily after download, especially if stored in `.mbox` or `.eml` formats. That’s why they are viewed with more caution in legal settings.

Conclusion

Yes — emails downloaded into Outlook, even from Gmail, are generally accepted as legally valid, provided the headers are intact and the file has not been manipulated. Outlook's storage format and market reputation contribute to its legal trustworthiness — even without Exchange.

If you want to achieve similar legal credibility with Thunderbird, the focus should be on:

Enforcing DKIM-signing (from Gmail, already done) Locking down `.eml` or `.mbox` file access Possibly archiving in tamper-evident formats

Let me know if you’d like a workflow to export Thunderbird emails into a legally robust format similar to `.pst`.

When I use Mozilla's VPN service...many mozilla vpn servers will block me from sending out emails giving this error message:

Sending of the message failed. An error occurred while sending mail. The mail server responded: Service unavailable; Client host [23.234.88.xxx] blocked using clients.rbl.e-scout.net; host 23.234.88.xxx blocked due to abusive behavior from your network. Please contact servers@ispn.net for resolution.. Please check the message recipient "xxxxxxx@xxxxxxxxx.com" and try again.

Mosilla's VPN service is blocking its own Thunderbird software from functioning...lolol Are you going to fix this Mozilla??? Looks like you're tripping over your own feet...

When I attach a pdf to an email I'm writing I'd like to be able to open it to check it's the right one, but since I updated it won't work, I get the message as per attached. Excel and Word documents no problem.

Hi, our city provides a garbage/recycling calendar (weekly) that is added into Google calendar by a url. On my first laptop, when I installed Thunderbird and setup the calendar, the entries showed up (as well as other Google calendar entries). On my 2nd laptop, they don't show up, although other google calendar entries do. Any ideas? Thanks, Shawn

I use many filters to divert many incoming emails to nominated local folders. One filter only started misbehaving last year. It transfers the message but then enters random number of duplicates so filling the folder with garbage. The message gets duplicated 1,2,3,4 times at random.

How can I cure this?

Hi there,

Every time I try to use my emails on Thunderbird, it says it is not connected to the server.

Could you help with this, please?

My emails are: m.ragab@arabic-englishlanguageservices.co.uk info@arabic-englishlanguageservices.co.uk

Regards, Mohamed

According my settings the junk mails in junk folder should be deleted after one day. But - instead of deleting these junk mails - the junk mails just move to trash folder (which then must be cleared manually) - absolutely nonsense !! My thunderbird version 139.0.2 - before update to this current version, the junk mails have been DELETED (!!) according my settings and NOT moved to trash

Unable to log in at server. Probably wrong configuration , username or password. Old computer went kaput have a new one but I am now unable to log into mt email account

Regarding: Thunderbird Version 128.11.1esr 　 Please tell me how to make folder pane wider than the system default width of the vertical layout. The reason of this question is that I cannot see full of folder names under the system default width.