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Hello!

I just observed a new issue with S/MIME. When trying to send an encrypted mail to somebody new, I get an error “End-to-end encryption requires resolving certificate issues with somebody@example.com”.

The message is not very helpful, and doesn’t propose any solution. So a web search gave me this article: Prerequisite for sending an encrypted email message. It states:

> If Thunderbird considers the email's signature and the sender's certificate valid, it will automatically be imported and available when you attempt to encrypt an email to that correspondent using the S/MIME technology.

When I open the sender’s mail, the signature is confirmed as valid by Thunderbird.

Ignoring the warning message and trying to send the encrypted mail results in the following error in the log: `mailnews.send: NS_ERROR_ILLEGAL_VALUE: Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIMsgComposeSecure.beginCryptoEncapsulation]`

So, I verified in my list of certificates for people, and that new person didn’t figure in the list. Other people did, the last one from 6 June.

Is it possible there’s a bug causing TB to not import the certificate when I open the mail? What would a workaround be? Is there a way to import a sender’s certificate manually from their signed mail?

Over a month ago I began experiencing an error message when attempting to send emails from my gmail account using Thunderbird (TB). Error msg reads: Sending of the message failed. An error occurred while sending mail. The mail server responded: Must issue a STARTLS command first. For more information go to: https://support.google.com/a/answer/3221692 and review RFC 3207 specifications. 00721157ae682-765bb916a90sm38332507b3.4-gsmtp. Please verify that your email address is correct in your account settings and try again.***While I have looked at all of this, I can't really find a solution I know how to implement.***

I can send emails using Google webmail and when I do, the emails show up in my TB Sent items folder. I'm totally stumped and considering moving to Outlook. But TB has been perfect for me for years and I want to stay with it. Any help will be much appreciated!

Hello, Since last night, we've been receiving illegible and encrypted emails, as shown in the attached screenshot. Please help us resolve this problem, as we are professionals for whom emails are vital. Thank you in advance. Sincerely, G.BOSSERT ITD

Hi All. New to Thunderbird but liking what I see. Am trying to install a new certificate but keep seeing the same error message when I attempt to send an email:

Sending of the message failed. You specified that this message should be digitally signed, but the application either failed to find the signing certificate specified in your Mail & Newsgroup Account Settings, or the certificate has expired.

So here is what we know:

The certificate seems to work (I've sent test emails to a couple of test email accounts) when I use it in Outlook safe mode. Can't get it to work in normal Outlook mode because of add-ins, hence my switch to Thunderbird. They seem to appear fine in the S/MIME section for digital signing and encryption and I can even see the certificate when I go into Manage S/MIME Certificates.

Has anyone come across this before / got any ideas about how to resolve this? Thanks!!

A few days ago I stopped getting my mail. I checked to see if the firewall was set to allow Thunderbird. It was. I tried changing account settings. I found out that if I changed Connection Security from STARTTLS to SSL/TLS there was no change. But, if I went to NONE my mail came through. Fine, but I don't want to go on without Security. Any suggestions?

Ed

With the latest updates, the client no longer accepts the self-signed smtp certificate as exceptions. The server is old and there is no way to upgrade to a newer one. It is also not possible to connect a third-party certification authority

I need help with fixing certs I beleive were changed by an application. I found some files in an application I installed through another without fully looking at the extra packaged material. One seems to be a configuration file for CA certs and the other is a list of SSL certs taken from Mozilla that were included with the intent of editing trusted user certs. I now see the evidence of a Linux device using my Firefox. To me, that is pretty clear evidence that Shell was used for some connection. So, with that, I'm assuming the certs on my device are not correct, and need to be fixed. Please let me know what I can do for this and if there is any other information you can give me on how to find out more about what to do. Unfortunately, there are also files that seem to also change user to a fake user while they gain root as guest. Any additional information including removing and replacing all certs wouldbe very helpful. Im trying to get to a certain point of restricting access and making a move to alert the correct people in Github and a couple of others with/towards some of the files before I do any kind of reset as I am not fully sure how tainted the restore might be.

My mail provider requires the usage of portnummer 143 together with encryption method SSL/TLS. Thunderbird automatically uses encryption method STARTTLS when port # 143 is entered. This is according to the recomended usage of special port numbers, but I need no correction from thunderbird, when my stupid provider wants to use ist differently.

Good morning

Thunderbird is not sending or receiving emails, i already deleted the gmail account and reinstalled it but it didn't work upon installation i get the attached message.

this was running on a windows 7 pc with no issues for about 2 years.

thanks in advance

Trying to enable NextDNS for DNS over HTTP but it shows as not active (TRR_PARENTAL_CONTROL). I do not have any parental controls enabled on this device so im not sure whats causing this isssue.

I am using an email server that currently is using certificates that have expired. That problem is being worked on. In the meantime, whenever I access the server to open a folder, I get a pop-up notification telling me that the certificate has expired. I go ahead and confirm the security exception and check the box to permanently store the exception. Trouble is this ISN'T being persisted, when I open a different folder I have to go through this process again in order to access my emails in that folder.

Me thinks you got a bug in your software Kemosabe!

Hi,

I need to ask regardining this security.cert_pinning.enforcement_level. how can i set this value using the windwos server GPO? i could not find this even after copying the firefox.admx file. could someone please guide me how can i acheive it?

I would really appreciate the help!

Regards Sheras

On Monday, 17 November 2025 the Security Certificate expired and I stopped receiving emails both on my computer and Andriod Device. As a result I am not receiving any emails through Thunderbird, but I can go to email host site to view them.

I logged in my computer tonight and clicked here and clicked there and the error message: "The certificate for mail.homebizmall.net is not valid for that server. Someone could be trying to impersonate the server. Create an exception but this could mean that someone has stolen your certificate and may be able to impersonate you."

So it seems the POP server and the SMTP server certificates were only valid for 3 months and I was FORCED to create the exception for both servers. Now I am worried the security has been breached.

By clicking here and clicking there, I stumbled on a few people who seem to have this problem, but each with their own limitations. My operating System is Windows 10 without the option to upgrade. I have not extended the security updates because I don't understand if it is just the operating system uploading to the cloud or everything on my computer and I am not prepared to do the latter.

Is it safe to leave the band aid on that I have used for the moment? Can I create an exception for the phone? Or is there a glitch that someone needs to walk me through fixing?

Thanking you in advance

Clinton

I used Chrome until two days ago. I just got tired with how shitty the browser was, how bloated it made my computer, and how much Google treats everyone like a data product. However, I use hella google systems from Voice to Chrome to Drive to more and it all worked great together. Choosing to change to Firefox wasn't an easy decision but I knew it was a good one

Which makes it super irritating that some of the functionality is already facing problems. I have shortcuts I built to make it easier to study or do random things so I don't get distracted or tired. One shortcut is clicking a key that should launch UWorld in my default browser & use Lastpass to autologin (I couldn't get it to launch the service but that was a separate issue).

I check if autologin was on for the password on LastPass I've allowed all permissions to the LastPass extension I clear my cookies on UWorld & turned off enhanced tracking protection for the UWorld login portal site

What should I do to fix my one button shortcut again?

I really don't want to go randomly turning off every protection that Firefox gives me to figure it out so I'd appreciate someone who understands the browser better helping me out. Also, bonus points if you can help me build a single shortcut button on my Mac that can launch UWorld & navigate me straight to the question bank. (I do think the issue with autologin on LastPass is going to become more of an issue as I start opening up more websites I used to use on Chrome so I'd rather nip it in the bud before I see the problem occur more often)

I can't send mail via smtp.comcast.net. I can connect to IMAP and get mail, and I can send from my iphone and (new) Outlook. Running TB v142.0 (64 bit) on Windows 11. Issue is reproducible on second system. When I try to send mail, client tries for 1 minute, then times out with "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.comcast.net timed out. Try again."

TB log says: 14:17:11.775 1756750631775 addons.xpi WARN Checking C:\Program Files\Mozilla Thunderbird\distribution\extensions for addons 14:19:37.714 mailnews.smtp: New client instance SmtpClient.sys.mjs:121:17 14:19:37.716 mailnews.smtp: Connecting to smtp://smtp.comcast.net:587 SmtpClient.sys.mjs:141:19 14:19:37.799 mailnews.smtp: Connected SmtpClient.sys.mjs:429:17 14:20:39.211 mailnews.smtp: NetworkError: a Network error occurred SmtpClient.sys.mjs:476:17

   _onError resource:///modules/SmtpClient.sys.mjs:476

14:20:39.212 mailnews.smtp: Socket closed. SmtpClient.sys.mjs:550:17 14:20:39.214 mailnews.smtp: SecurityError info: PR_END_OF_FILE_ERROR SmtpClient.sys.mjs:491:21 14:20:39.245 mailnews.send: Sending failed; The message could not be sent because the connection to Outgoing server (SMTP) smtp.comcast.net timed out. Try again., exitCode=2152398868, originalMsgURI=imap-message://mgiul%40comcast.net@imap.comcast.net/Drafts#57692 MessageSend.sys.mjs:343:32

smtp.comcast.net is using a self-signed cert. Is this the problem? C:\Users\rchar>openssl s_client -starttls smtp -connect smtp.comcast.net:587 Connecting to 96.103.145.180 CONNECTED(000001F8) depth=3 C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services verify error:num=19:self-signed certificate in certificate chain verify return:1 depth=3 C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services verify return:1 depth=2 C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority verify return:1 depth=1 C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA verify return:1 depth=0 C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net verify return:1 --- Certificate chain

0 s:C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net
  i:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA
  a:PKEY: RSA, 2048 (bit); sigalg: sha256WithRSAEncryption
  v:NotBefore: Jan  6 00:00:00 2025 GMT; NotAfter: Jan  6 23:59:59 2026 GMT
1 s:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA
  i:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority
  a:PKEY: RSA, 2048 (bit); sigalg: sha384WithRSAEncryption
  v:NotBefore: Feb 12 00:00:00 2014 GMT; NotAfter: Feb 11 23:59:59 2029 GMT
2 s:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority
  i:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services
  a:PKEY: RSA, 4096 (bit); sigalg: sha384WithRSAEncryption
  v:NotBefore: Jan  1 00:00:00 2004 GMT; NotAfter: Dec 31 23:59:59 2028 GMT
3 s:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services
  i:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services
  a:PKEY: RSA, 2048 (bit); sigalg: sha1WithRSAEncryption
  v:NotBefore: Jan  1 00:00:00 2004 GMT; NotAfter: Dec 31 23:59:59 2028 GMT

--- Server certificate

MIIHATCCBemgAwIBAgIRAJUASDPOQisnR1zo9CfhXcYwDQYJKoZIhvcNAQELBQAw gZYxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAO BgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMTwwOgYD VQQDEzNDT01PRE8gUlNBIE9yZ2FuaXphdGlvbiBWYWxpZGF0aW9uIFNlY3VyZSBT ZXJ2ZXIgQ0EwHhcNMjUwMTA2MDAwMDAwWhcNMjYwMTA2MjM1OTU5WjBdMQswCQYD VQQGEwJVUzEVMBMGA1UECBMMUGVubnN5bHZhbmlhMRwwGgYDVQQKExNDb21jYXN0 IENvcnBvcmF0aW9uMRkwFwYDVQQDExBzbXRwLmNvbWNhc3QubmV0MIIBIjANBgkq hkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoLkgKQUqw4MylCObwwzTyFkIoMN/NRNl 6EY0zS+sjlYMFPplSULdfqs1tEcWZhCs+u1EkJN9+/juCtzeZ9c73yx8nTph0/KZ 5ri9t55yu5xhtuDv2WsMJmqcTOHPXRSZt7abpsvNfxCb6IG2YdPrBNqPyZPEJ6jn h3CY3qBbsreL4iR+UEGunSJAg2mRXHhx0/aYN3CTUetOcSBzIwoFXPklptWCcm5V knK+BWqFtKlyt6nHW/o2qK74nLDgKNUgxR9pG/Bw48ZER1emGsNlN2RVyOBtoAAG 15x4vD2iFBVEe9A0q9HOJc9bGSNb6zuU4ZpCb+RpNq3kkqJCpS6aJwIDAQABo4ID gDCCA3wwHwYDVR0jBBgwFoAUmvMr2s+tT7YvuypISCoStxtCwSQwHQYDVR0OBBYE FHz0nGUjqJ0rg0OQFz/hLkJ581OVMA4GA1UdDwEB/wQEAwIFoDAMBgNVHRMBAf8E AjAAMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcDAjBKBgNVHSAEQzBBMDUG DCsGAQQBsjEBAgEDBDAlMCMGCCsGAQUFBwIBFhdodHRwczovL3NlY3RpZ28uY29t L0NQUzAIBgZngQwBAgIwWgYDVR0fBFMwUTBPoE2gS4ZJaHR0cDovL2NybC5jb21v ZG9jYS5jb20vQ09NT0RPUlNBT3JnYW5pemF0aW9uVmFsaWRhdGlvblNlY3VyZVNl cnZlckNBLmNybDCBiwYIKwYBBQUHAQEEfzB9MFUGCCsGAQUFBzAChklodHRwOi8v Y3J0LmNvbW9kb2NhLmNvbS9DT01PRE9SU0FPcmdhbml6YXRpb25WYWxpZGF0aW9u U2VjdXJlU2VydmVyQ0EuY3J0MCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5jb21v ZG9jYS5jb20wggGABgorBgEEAdZ5AgQCBIIBcASCAWwBagB2AJaXZL9VWJet90OH aDcIQnfp8DrV9qTzNm5GpD8PyqnGAAABlDwZ58gAAAQDAEcwRQIhAOgI6NbRS4t6 9XvPVbmFixPHyFJXDqU60dv5r+RB9Y9YAiAwlfQhXe45ccND3T5te2KryuxvRhzW aBO3oIS6ixw6DAB3ABmG1Mcoqm/+ugNveCpNAZGqzi1yMQ+uzl1wQS0lTMfUAAAB lDwZ56oAAAQDAEgwRgIhAKmynGx19jBgk4Xy/eChCKjR/vpOtCH16470/jJyY6Yy AiEAkwlRN7Cn1AN20CGjNowsJ2PBaqNOk/u297W/RttgBKMAdwDLOPcViXyEoURf W8Hd+8lu8ppZzUcKaQWFsMsUwxRY5wAAAZQ8GefaAAAEAwBIMEYCIQDyR2Zz3Spd 0Gul6Z2dJa15aUEiEaW7KEAtbCcqz/zoLwIhAIV8YxWeI8rVaAvdl9kWquejUOTx M2G4iYjeZINb1VMgMEMGA1UdEQQ8MDqCEHNtdHAuY29tY2FzdC5uZXSCEHNtdHAu eGZpbml0eS5jb22CFHd3dy5zbXRwLmNvbWNhc3QubmV0MA0GCSqGSIb3DQEBCwUA A4IBAQBgn3Z51e8DZ/bO/AFqc22A4e5EqfUx4y6itcaz3mnQcU9pAsA/LK/WeY+e PtHIkWNKFlysJSbU2ByJ/6+bnebalXgRZ3sAeB2Z7UIUIHEjhcEQE2s4CxAXBiI7 SgqWjrw/Qj+AOghhMwayhIjmnNk34MmyY4f9KsAC6fIEn9ypCxuaN4lrwZcmS8iK o6PRho6pd837BEaRNIZBQpI/8WKxoKsNOu8bw8FwX/Zn8q+1oPo+0sQkmSmWOruu l8tlq8boA5R6YSBWek8hxmEZppvBs55wfNCnr2DQ4CgAREJZMKt6PIiKlgQ9r58b OSb5otnW7xsrx3SKM2zlvRA5mhfL

subject=C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net issuer=C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA --- No client certificate CA names sent Peer signing digest: SHA256 Peer signature type: rsa_pss_rsae_sha256 Peer Temp Key: X25519, 253 bits --- SSL handshake has read 6708 bytes and written 1662 bytes Verification error: self-signed certificate in certificate chain --- New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384 Protocol: TLSv1.3 Server public key is 2048 bit This TLS version forbids renegotiation. Compression: NONE Expansion: NONE No ALPN negotiated Early data was not sent Verify return code: 19 (self-signed certificate in certificate chain) --- 250 OK --- Post-Handshake New Session Ticket arrived: SSL-Session:

   Protocol  : TLSv1.3
   Cipher    : TLS_AES_256_GCM_SHA384
   Session-ID: 27FBCE0D025BF752A9F038657257E923F1E5560B92BB78A47C5C9E0FFFDBEF7B
   Session-ID-ctx:
   Resumption PSK: FAFF92690FBEDF157D2856329FDABB033F2A0948C5A0F668E4B69C197EC6E52B8DE8A676EA4A78EAEEED7E90C4935DEC
   PSK identity: None
   PSK identity hint: None
   SRP username: None
   TLS session ticket lifetime hint: 300 (seconds)
   TLS session ticket:
   0000 - 97 cc 16 34 49 69 e3 c2-8f 6b ab cb e0 53 cb c1   ...4Ii...k...S..
   0010 - e0 31 10 bf c8 94 c5 d1-59 2b 3e 84 f7 63 44 be   .1......Y+>..cD.
   0020 - 3e d6 69 b0 d4 10 7a 1a-4f 6a da 21 91 6b 34 f2   >.i...z.Oj.!.k4.
   0030 - 1c 2c df cc 5f ee b5 ce-4c 71 49 b0 28 d6 7b 92   .,.._...LqI.(.{.
   0040 - 9e 6a dd bb 93 ca 9e 44-80 1f df ec f7 e4 95 04   .j.....D........
   0050 - 7c c1 6b 1d 86 59 7c 18-7d 98 41 0d 04 a1 f1 ae   |.k..Y|.}.A.....
   0060 - 7b 6d 68 ad 68 a6 b2 32-95 71 d3 89 09 ea 28 7c   {mh.h..2.q....(|
   0070 - ee 8f 67 1e ab e6 09 d7-5d c6 67 0d 0e 63 7b 24   ..g.....].g..c{$
   0080 - 87 cc fb eb 8f a8 c6 67-60 d2 70 e6 58 93 06 d0   .......g`.p.X...
   0090 - 1f ef 95 15 53 92 95 19-85 76 91 26 7c a1 9e 96   ....S....v.&|...
   00a0 - 12 9d bd b2 a9 38 45 05-a5 28 14 65 4c ac c0 6d   .....8E..(.eL..m
   00b0 - c6 65 e7 b8 4b ff 0c dd-58 82 c9 c5 de 8d 64 ab   .e..K...X.....d.
   00c0 - f4 59 c5 5c bc bd c2 e9-34 2a d7 a7 99 21 97 60   .Y.\....4*...!.`

   Start Time: 1756752732
   Timeout   : 7200 (sec)
   Verify return code: 19 (self-signed certificate in certificate chain)
   Extended master secret: no
   Max Early Data: 0

--- read R BLOCK --- Post-Handshake New Session Ticket arrived: SSL-Session:

   Protocol  : TLSv1.3
   Cipher    : TLS_AES_256_GCM_SHA384
   Session-ID: 13DA31F60D1C9A3207FFEA54D2CEC29BB0D44016068E3E79A18492F695B02E80
   Session-ID-ctx:
   Resumption PSK: 44D18B4AEB19CDEBA968E3BD867C3B0167C07C61DC3091072882660FC234D4B3B071B663546C5B4AC3E53A6A5C206A9B
   PSK identity: None
   PSK identity hint: None
   SRP username: None
   TLS session ticket lifetime hint: 300 (seconds)
   TLS session ticket:
   0000 - 97 cc 16 34 49 69 e3 c2-8f 6b ab cb e0 53 cb c1   ...4Ii...k...S..
   0010 - 09 52 42 f9 c9 f7 bc 99-5a b5 73 e3 9b b8 1c 91   .RB.....Z.s.....
   0020 - 16 f5 ea 33 20 29 e1 59-79 65 46 0a 4b ad b7 fe   ...3 ).YyeF.K...
   0030 - b4 aa b7 7b f8 57 36 10-71 09 19 c6 d2 64 c4 8a   ...{.W6.q....d..
   0040 - 47 f6 28 4b 62 9e be ca-d9 16 1a e7 df 7d 51 f7   G.(Kb........}Q.
   0050 - f6 66 04 fe 37 cf 0c bb-4f d8 d3 1b d6 06 be d0   .f..7...O.......
   0060 - 21 ee 9e 65 ac a3 18 80-31 b7 17 5b 23 d2 9d 4e   !..e....1..[#..N
   0070 - 57 f7 b0 66 01 5f cc c5-a1 a5 96 ee d2 d8 55 ed   W..f._........U.
   0080 - 5b 91 86 da 91 d5 3d 17-36 bd a5 97 58 ab fb ad   [.....=.6...X...
   0090 - eb eb 38 5e fd e3 7a 13-b9 f8 5c 14 f5 80 3a 72   ..8^..z...\...:r
   00a0 - 52 66 d9 23 8c a3 50 5c-3c e5 fc cb 22 21 11 3f   Rf.#..P\<..."!.?
   00b0 - a6 71 87 67 8b 33 8e b0-0a 65 46 f6 df 7a f0 f3   .q.g.3...eF..z..
   00c0 - 04 4e cf 22 ad 4d 45 69-53 9c 45 56 df 07 ae e3   .N.".MEiS.EV....

   Start Time: 1756752732
   Timeout   : 7200 (sec)
   Verify return code: 19 (self-signed certificate in certificate chain)
   Extended master secret: no
   Max Early Data: 0

--- read R BLOCK closed

C:\Users\rchar>

I keep getting a certificate error on my Thunderbird. The certificate refers to an email account i no longer have (Personal domain) and i have removed the account in thunderbird, and also removed previous certificate exceptions.

I have been through all menus and settings, and cannot find anywhere where it refers to that domain (and subdomain) I have also removed one entry with that FQDN in the outgoing server section.

What to do?