I run a Mailcow-Instance under eg. mail.main.com and have configured another Domain secondary.com under “Configuration –> Mail Setup” which I’d like to use for sending/receiving mails.
Adding a new account to Thunderbird which checks the certificate of secondary.com:143 results in an error: The certificate belongs to another website. (Screenshot). Ignoring the certificate error and sending a mail to some Mail-Tester Website results in a decent score.
The command openssl s_client -starttls smtp -crlf -connect secondary.com:143 gives following output:
CONNECTED(00000003)
Didn't find STARTTLS in server response, trying anyway...
140555206051136:error:1408F10B:SSL routines:ssl3_get_record:wrong version number:../ssl/record/ssl3_record.c:331:
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no peer certificate available
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No client certificate CA names sent
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SSL handshake has read 228 bytes and written 342 bytes
Verification: OK
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New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
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I am running the WebUI behind the traefik reverse proxy und use certdumper to extract and insert the certificate (of mail.main.com!) at ./data/assets/ssl/
Further i appended a screenshot about my DNS-Configuration which seems to be fine.
Any help appreciated 🙂, since I am running out of ideas
Kind Regards
David