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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?

Thunderbird will not download mail. It sends this: "The certificate for inbound.att.net does not come from a trusted source." "Location: inbound.att.net:995" Then it sends the data with the certificate information. I am not a programmer, I do not understand what I am supposed to do to get it going again.

AVG sends message: "We've identified a site certificate problem" "Trust for this certificate has been revoked."

Looking at certificate page that AVG provides is Greek to me. General tab displays:

"This certificate has been revoked by its certification authority"

issued to : inbound.att.net

issued by: Digicert Global G2 TLS RSA SHA256 20250 CA1

Valid from: 4/12/26 to 10/28/26

Details tab:

lists a bunch of things that I don't comprehend and offers an option to "copy to file" and lists a number of formats to copy the file to.  Have no idea which would be the one to use. 

Trying to access email directly from browser has not been successful because it wants verify my identity by sending message to my phone, but it does not send anything.

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.

My system • Windows 11 on a Dell laptop. • Firefox Version 157, my default browser. • Norton 360 Standard. • Two Firefox profiles; the warning appears in both. • Firefox Troubleshooting Mode does not eliminate the warning https://support.mozilla.org/en-US/kb/sslkeylogfile-warning?utm_source=chatgpt.com

What I have observed The warning appears on Firefox network-error pages, including when the internet is disconnected or I enter an incorrect URL. A particularly reproducible example occurs after I successfully log in to Kotak Net Banking and select Help → Raise a Query. Firefox then displays a connection/privacy warning associated with the embedded page. I do not see the same behaviour in Chrome or Firefox Private Browsing when performing the equivalent Kotak steps. Troubleshooting already completed 1. Norton Safe Web HTTPS scanning was disabled and re-enabled without resolving the issue. 2. QUIC/HTTP3 scanning, WebSocket Protocol Scanning and DNS/DoH scanning were individually tested without resolving it. 3. Firefox Enterprise Policies are inactive. 4. I found no SSLKEYLOGFILE entry in either Windows User Variables or System Variables. 5. Norton and Dell malware scans found no malware. 6. The warning also occurs when I connect through a mobile phone hotspot rather than my usual BSNL connection. Questions for Mozilla's technical contributors 1. Does this warning establish that Firefox detects SSLKEYLOGFILE, or could another mechanism produce the same message? 2. Can the variable be inherited by Firefox from a parent process or injected into its running process even when it is absent from the Windows User and System Variables? 3. What is the safest way to identify which process or security product is setting it on Windows 11? 4. Is there a known interaction between Firefox 157 and Norton 360 Standard that could explain this behaviour? 5. What evidence should I collect to distinguish a Norton issue from a Firefox issue without disabling security protections or modifying Windows settings? I am not looking to disable security features indiscriminately. I want to identify the actual cause and, if Norton is responsible, determine the precise setting that needs attention. I would particularly appreciate a response from a contributor with Windows networking, Firefox TLS or security-software diagnostic experience. Thank you.

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?

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

https not recognized by Firefox in 151 Thunderbird on silicon iMac with Sonoma. Tried & checked many solutions with no results.

Firefox browser primary , always Nothing in Modified Important Preferences With Extensions off still a problem

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

Thank you. I’m not a technical person and so could you please share the specific and safe steps which will resolve both the error state shown, and the TLS logging issue without creating any other unintended consequences. I don’t want create any additional problems while trying to address these two issues. Thank you

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 -

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

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

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

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.