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I've finished setting up the S/MIME encryption in Thunderbird, and imported all the certificates needed. When people with the certificates emailed me, I could receive and read all the emails. However, when I replied to the same people, I got the error message saying 'End-to-end encryption requires resolving cerficiate issues'. My colleagues imported the same certificates without any issues. Do you have any suggestions for me to solve the issue? Thank you very much!

I recently encountered an issue when attempting to login to The Coventry Building Society website using Firefox (desktop PC & Windows 10):- https://www.coventrybuildingsociety.co.uk/ It failed to display the page used to enter the one time passcode used for two factor authentication.

After looking on some forums I discovered this is because 'Strict' tracking protection was enabled. If I change to 'Custom' and uncheck 'Tracking Content' then things work as expected.

I also read on a forum that you can leave tracking protection set to 'Strict' but enter the URL for the problem website under 'Enhanced Tracking Protection -> Manage Exceptions'. I tried entering 'https://www.coventrybuildingsociety.co.uk/' Initially this appeared to work. However, when I tried it again the following day, the page failed to load as before. I had to change back from 'Strict' to 'Custom' and uncheck 'Tracking Content' once again. It's as if the exception URL is ignored in 'Strict' mode.

Am I doing something wrong or is this how it is supposed to work? Do I need to click on the shield icon (to the left of the padlock icon) and turn off 'Enhanced Tracking Protection' every time I visit the website?

I am able to receive emails on Thunderbird but I am not able to send emails to anybody from Thunderbird. That happens on two computers I have. I am able to send emails from Outlook. Therefore, it is not my email provider's (BluePeak) problem. When I try to send an email from Thunderbird, I receive the following error message: “Sending the message failed. SSL received a record with an incorrect Message Authorization Code. The configuration related to must be corrected.”

Please help me resolve this issue. Thank you very much!

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.

Thunderbird says this "the certificate for imap.supanet.com does not come from a trusted source". however I have used this email for some time and am happy with it . can I continue with this certificate as I do trust this source

I am using a E-mail server that uses LetsEncrypt certificates. I was using Thunderbird 128 ESR without problems. When the certificate was updated, I was requested to confirm - then sending E-mails was possible. Now I have updated to Thunderbird 140 ESR. The E-Mail servers LetsEncrypt certificate was now updated but in Thunderbird I do not get any information about this, nor get I requested to check the new certificate. The SMTP connection just fails. The IMAP access to the E-mail server works fine. (IMAP and SMTP work both fine with K9-Mail on my mobile device)

How can I get Thunderbird to ask me again to check the updated certificate?

When my message filter uses the "Reply with Template" action, the reply e-mail is always PGP encrypted, even when I do not have any public key for the recipient e-mail address. As a result, the reply e-mail is always corrupted.

I am using Thunderbird 140.7.1esr on Windows 10.

I have attached a screenshot of what the reply e-mail always looks like.

In the Template that I am using, the "encrypt" button is not selected, and in the OpenPGP menu of the Template, the "Encrypt" menu item does not have a checkmark next to it.

Does anyone know how I can get Thunderbird to send reply e-mails without using encryption?

I have spent some time digging through your messages about how to fix this issue. I get the general "where to" enable SSL/TLS but no trouble shooting to this specific level.

Spectrum (charter) Internet on May-30-25 a pop up "Add Security Exception" on wife's account (Image #1 below). We have same Internet provider and same server config's (except email name & password or course).

 This Security Exception has happened before, as well as on my account in the past. 

Although, I never got the Exception this time. We did "Confirm Security Exception" 2x on her account and she is up and running again. No issues.

  However, I can't receive e-mails with the Account Settings / Server Settings / Security Settings

"Connection Security" set to SSL/TLS" it must be set to "None" When set to SSL/TLS and I push the "Get Mail" button, the server isn't even banged as there's no msg in lower left frame of TB. I have gmail account and it does bang that one like it should. If set to "None" I get the msg in lower left TB frame showing connection to Charter server and I receive any outstanding e-mails. But I don't want to continue without a password.

 Under [Settings/ Privacy & security / Manage Certificates]

hers (Image #2 below) looks different than mine (Image #3 below). She has the 2 confirmed Security Exceptions, but also has a "View" and "Export" button that are bolded when the specific line item is highlighted. I do not have a View or Export button shown. How do I enable the SSL/TLS with password and actually receive emails?

 I am using TB 128.11.0esr (64-bit)

thx in advance Gene

I have suddenly started to receive this message when I open Thunderbird "Certificate for IMAP Gmail does not come from a trusted source". When I click on this message I get the attached screenshot.

I've gone through the forums by I can't understand what it is written. It seems like everything that is written is designed for people who have a good understanding of technology. I don't but I was able to determine that the OAuth is properly set.

I am using 128.14.0esr (64-bit) Thunderbird for Linux Mint mint-001 - 1.0 Updates disabled by system administrator Currently on the esr update channel

Wir können wir die Verschlüsselung einer Nachricht aktivieren? Diese ist bei uns durchgestrichen und lässt sich nicht auswählen. Da wir oftmals Befunde verschicken müssen und den Datenschutz nicht verletzten wollen, würde wir gerne die Option der verschlüsselten Nachricht nutzen wollen. Bitte um Hilfe diesbezüglich, danke.

I have added a certificate to the Thunderbird Certificate Manager (localcert.png), with the info as shown in certdetails.png. However, Thunderbird is not sending the certificate. I have "When a server requests my personal certificate" set to "Ask me every time". I also tried choosing "Select one automatically" but that did not change the result.

However, my mail server, which uses TLS client certificates as one factor in sender authentication says: May 27 02:00:05 Mercury2 smtpd[9850]: b972fe936721dfe0 smtp disconnected reason="io-error: handshake failed: error:0A0000C7:SSL routines::peer did not return a certificate"

What am I doing wrong in the config that is causing Thunderbird to not send the certificate?

Details of SW in use: OS Ubuntu 24.04.2 LTS Mail server OpenSMTPD opensmtpd-7.6.0,1 on FreeBSD Thunderbird 128.10.2esr (64-bit) installed from snap $ snap info thunderbird name: thunderbird summary: Mozilla Thunderbird email application publisher: Canonical✓ store-url: https://snapcraft.io/thunderbird contact: https://www.thunderbird.net/contact/ license: unset description: |

 Thunderbird is a free email application that’s easy to set up and customize
 - and it’s loaded with great features!

commands:

 - thunderbird

snap-id: k1Ml1O9GzSO2QftV0ZlWSbUfQ78nN460 tracking: latest/stable refresh-date: 3 days ago, at 10:48 MDT channels:

 latest/stable:    128.10.2esr-1 2025-05-23 (734) 220MB -
 latest/candidate: 128.11.0esr-1 2025-05-23 (735) 220MB -
 latest/beta:      139.0b4-2     2025-05-20 (731) 236MB -
 latest/edge:      ↑                                    

installed: 128.10.2esr-1 (734) 220MB -

Bonjour

Depuis quelques jours je rencontre le message suivant:

L’envoi du message a échoué. Une erreur est survenue lors de l’envoi de l’e-mail. Le serveur e-mail a répondu : 1jHjuyBzCXgNw StartTLS obligatoire. StartTLS mandatory.OFR303_199 [199]. Veuillez vérifier que votre adresse e-mail dans les paramètres du compte est correcte et essayer à nouveau.

Dans les paramètres du compte tout semble OK Merci pour votre aide Cordialement

Hello, My SMTP server uses Let's Encrypt certificate. The website with the same domain has no certificate. Thunderbird refuses to connect to my SMTP server. Test connection to the server (STARTTLS) in account settings sais "The secure connection to the server failed" (or similar. I see bg localization). Another server with Let's Encrypt certificate. Test pases. Clicking View certificate shows webserver cert (from DigiCert Inc).

I can't send emails! :)

Regards! Valentin

Hi

Last week we started having issues sending emails from our Thunderbird account (Optus email). When you go to press send we see a Add Security Exception pop up. When I click View we see the Issuer Name is DigiCert Inc. When I click Get Certificate it says No Information Available. We checked the SMTP setting with Optus today and they are correct.

Description: Optus Account Server Name: smtp.optusnet.com.au Port: 25 Connection Security: STARTTLS

If anyone has any ideas that would be great. Thanks Alysha

I received a PGP-encrypted e-mail which is just showing the encrypted text in mail preview and also in a separate mail window; it is not getting auto-decrypted, even though the correct key is present in the OpenPGP key management. I have this same behavior on two different setups on Linux Mint 21.1 Vera. Once I reply to the e-mail, the original message gets decrypted in the reply message, but not in the original.

I've got another setup on MacOS, same Thunderbird version, which also does not auto-decrypt the message, but in message preview provides a button "Decrypt" which does the job. But this button is missing in the Linux configs.

All setups have the correct PGP Key configured.

Any hint to resolve the issue is highly appreciated. Thanks for your time.

i can not receive mails, since the update to 128.5.2ESR not on imap.strato.com not on imap.gmail.com not on mail.yourhosting.com

just since today after the update. sending emails seems to work.

I did NOT change anything in the accounts.

How to solve????

Thank you.

Typically if I experience a security certificate exception, thunderbird will popup the certificate exception box, I click to get certificate and am done.

Today I cannot get the certificate popup to appear. which is fine I know where the certificates are managed but I have not a clue how to add a certificate OR what information to enter into the "Add security exception" dialogue box

Any help would be greatly appreciated.

Hello.

I have added a new account to Thunderbird, and it is not syncing to show new messages. I am getting a pop-up from Tbird saying "The certificate for mail.newcreationloughborough.uk is not valid for that server ..." etc. I have gone through the procedure titled 'Troubleshooting email client warnings about invalid server certificates' to add Norton's certificate to my email app (as directed by the 'resolve' link in the 'Resolve email sync issues caused by certificate warnings' from the Norton EE Cyber Security add-on), and it tells me that the certificate is already installed.

What can I do next to get it to sync?

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?