==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version: 1.4.0 MARIADB edition.
- Deployed with: Downloadable installer.
- Linux/BSD distribution: Ubuntu 20.04.1 LTS (GNU/Linux 5.4.0-47-generic x86_64)
- Store mail accounts in which backend: MARIADB.
- Web server: Nginx
- Do not manage mail accounts with iRedAdmin-Pro
====

Hi, today, K-9 Mail showed me an error that the certificat is invalid. Thunderbird is not able to download new emails, though it didnt show me an error yet. The certificat works for the webserver and when I log in via the web interface, it shows me a new email the clients weren't able to show me.

I followed this blog post to get an error message, I am pasting it below. I hope someone can help me.

CONNECTED(00000003)
140492141061440: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 5 bytes and written 309 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)
---