I checked the following (according to your post)
1. In the path / var / qmail / control / there is a servercert.pem file with a private key.
2. The mail.mydomain.com.pem / file does not exist in the path / home / kloxo / ssl /
I tried to create SSL for mail.mydomain.com.pem and it didn’t help either.
How do I configure serverlink for servercert.pem?
Could it be related to DNS?
My server is VM on ESXi
I remember a few years ago I installed KOLXO-MR sending the e-mail worked.
Which I do not remember what version it was.