Thunderbird Community Forum

What do I do about this warning I am receiving when I refresh my inbox? "The certificate for pop.windstream.net is not valid. Someone could be trying to impersonate the server and you should not continue"

   Unable to receive new messages on my Thunderbird inbox for this warning

What do I do about this warning I am receiving when I refresh my inbox? "The certificate for pop.windstream.net is not valid. Someone could be trying to impersonate the server and you should not continue"

   Unable to receive new messages on my Thunderbird inbox for this warning

I have Thunderbird installed on Windows 11 along with Norton 360. Today, my connection to the AT&T e-mail server suddenly disconnected and I immediately got a pop-up notification that Norton detected a problem with a security certificate. When I inspected the details, it indicated that the certificate for inbound.att.net had expired (the range of valid dates on the certificate actually listed the current date as the last valid date). After several infuriating calls with AT&T support and Norton support, I figured out that simply disabling Norton e-mail protection allowed me to access my e-mail account.

Multiple web searches on similar issues suggested that since Thunderbird has its own certificate storage, fixing the problem involves locating the Norton certificate file and importing it using Thunderbird's certificate manager. Unfortunately, that solution appears to be applicable for first-time Thunderbird installation, and I when I tried it I was informed that the certificate was already installed. Another web search suggested that I should go to the Authorities tab and remove the entry for "Norton Email Protection". Unfortunately, the entry that I found was for "Norton Web/Mail Shield", which according to at least one source is not the same thing, so I am afraid to remove it.

So my question is has anyone else encountered this same problem, and is the correct approach to remove the Norton Web/Mail Shield authority before importing Norton's certificate file?

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AVG sends message: "We've identified a site certificate problem" "Trust for this certificate has been revoked."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

Thunderbird email says the certificate for my Shaw email server does not come from trusted source. The certificate looks fine. I cannot get Thunderbird to "Add exception". The certificate issue seems to be an intermittent problem since yesterday lunchtime. It started working again yesterday afternoon, but stopped working at lunchtime today. How do I stop this error?

Receive popup message: The certificate for mobile.charter.net does not come from a trusted source. In trying to send email, popup message: Sending the email failed. Peer's Certificate issuer is not recognized. The configuration related to mobile.charter.net must be corrected. Then it wants me to Add Security, Get Certificate.

Hi

I have a problem with Thunderbird which might be a bit niche but here goes...

The first attempt at sending an email fails as TLS Record Layer v1 is used, the mail server sees this and hard resets the connection so sending halts. See attached Wireshark trace screenshot "Failed".

If I retry the send again Thunderbird uses TLS Record Layer v1.3 and the email goes out ok. See attached Wireshark trace screenshot "Success".

If I send another message immediately no problem but if I wait 20-30 minutes the above cycle happens again.

I have set the minimum TLS version in the config to 1.3 (option 4) and restarted Thunderbird but this has not changed anything.

Any ideas how I can fix this? It's a pain because automated replies don't work.

Server Posteingang IMAP (empfohlen) imap.vodafonemail.de Ports für Posteingang IMAP SSL: 993 / TLS: 143

Server Postausgang SMTP smtp.vodafonemail.de Ports für Postausgang SSL: 465 / TLS: 25 oder 587

When adding a new email account, the built-in web browser launches and displays the OAuth screen. To verify the security of the destination site, I want to click the green lock icon in the URL bar to check the details, but I can’t click it.

Does a green lock icon mean a secure connection has been established?

Am receiving a message reading-

The certificate for imap.gmail.com does not come from a trusted source.

Why do I suddenly (from one day to another) receive the message: "Das Zertifikat für imap.gmail.com stammt nicht von einer vertrauenswürdigen Quelle."

when trying to downlowd messages from Gmail?

I have not changed anything at all.

Hello,

I am writing this message in regards to Thunderbird's GPG support after v68, in the last hope that someone suggests a solution that moves me away from version 68. I consider the current state broken.

My PGP keys reside on a Yubikey, but smartcard usage has been broken after v68, as none of the supposedly correct setups work. It should work pretty much out of the box, but it doesn't. The whole idea of moving away from Enigmail without having a properly, fully implemented support, including for smartcards, or at least for working with GPG, was utterly misguided, IMO, and broke the once nice client.

I enabled gpg usage and fetching in Settings, I imported my pubkeys to Thunderbird's PGP manager, then added my external key (with GPG). Everything looks fine. But when I click an encrypted message, I get "The secret key that is required to decrypt this message is not avaliable". Nah, it's available and it's there! The pinentry isn't appearing at all and this is the result. I believe this is TB's fault, as the pinentry correctly appears with everything else I do, also with TB 68 + Enigmail. The setup is the same. I am using the latest Gpg4win.

Settings:

mail.openpgp.allow_external_gnupg - true mail.openpgp.fetch_pubkeys_from_gnupg - true mail.openpgp.alternative_gpg_path - has no effect whether set or not

gpg-agent.conf:

enable-win32-openssh-support default-cache-ttl-ssh 900 max-cache-ttl-ssh 1800 no-allow-external-cache default-cache-ttl 300 max-cache-ttl 3000 ignore-cache-for-signing allow-loopback-pinentry

gpg.conf:

utf8-strings auto-key-locate local use-agent

FYI, adding "pinentry-program" has no effect on solving the problem, whether set or not.

Your suggestions are welcome!

On my Linux machine, I exported the public key for an email address in Thunderbird 140.8.0esr (64-bit) into a file. I transferred the file to my Windows 11 machine via Warpinator.

On the Windows machine I am running Thunderbird 148.0.1 (64-bit). In Account settings>End-to-End encryption, I click Add Key>Import an existing OpenPGP key>Select File to import, and then I select the file.

I get an error message: Error! Failed to import file.

I'm surprised. I would think that going from one installation of Thunderbird to another would work this way. I am concerned that I won't be able to read incoming encrypted emails without the key working.

Can someone help me?

I receive a lot of Thunderbird messages with this text (in French) :

"Le certificat pour imap.gmail.com ne provient pas d’une source sûre."

What I have to do please Thnx

Running Thunderbird 140.8.0esr 64bit Windows 11 Home, v25H2 932GB storage 32GB ram i7-13700k

Recently, I've started getting the following message every time I launch Thunderbird: "The certificate for imap.googlemail.com does not come from a trusted source."

Digging into details I get: "you are about to override how Thunderbird identifies this site" "Location: imap.googlemail.com:993" "This site attempts to identify itself with invalid information" "Unknown Identity. The certificate is not trusted because it hasn't been verified as issued by a trusted authority using a secure signature."

Digging deeper into the certificate I find the issuer is Bitdefender who I use for antivirus and VPN. However, the VPN shows no effect when enabled or disabled. The validity period is 2 Feb 2026 to 27 Apr 2026

l can get email, but cant send it. Is Bitdefender at fault?

I'm stumped. What should I do???

Thunderbird 140.7.0esr allows me to e-mail my OpenPGP public key to myself, but it doesn't seem to have any way for me to get access to my private key. I was wondering how to export keys? Thanks!

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?