Same for me. It really seems to te a gmail bug(?). Have no idea.

Hi all its not only gmail i have similar issue:

Proteus mail 15:49:49 postfix/smtp[27305]: A41B61DFC0ED: to=<vladoportos@post.sk>, relay=smtp-1.post.sk[85.248.69.170], delay=99643, status=sent (250 Ok: queued as C91522B871B7)
Proteus mail 15:49:49 postfix/smtp[27305]: Server certificate could not be verified
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate peer name verification failed for smtp-1.post.sk: CommonName mis-match: smtp-2.post.sk
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk: num=10:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk: num=10:certificate has expired
Proteus mail 15:49:49 postfix/smtp[27305]: certificate verification failed for smtp-1.post.sk: num=19:self signed certificate in certificate chain
Proteus mail 15:49:49 postfix/smtp[27305]: A41B61DFC0ED: host smtp-10.post.sk[85.248.69.128] said: 450 <info@bancodata.eu>: Sender address rejected: Domain not found (in reply to RCPT TO command)
Proteus mail 15:48:45 postfix/smtp[27305]: Server certificate could not be verified
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate peer name verification failed for smtp-10.post.sk: CommonName mis-match: smtp-2.post.sk
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk: num=10:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk: num=10:certificate has expired
Proteus mail 15:48:45 postfix/smtp[27305]: certificate verification failed for smtp-10.post.sk: num=19:self signed certificate in certificate chain

Just a quick note.

You can use smtp.gmail.com to relay your outgoing emails, but it seems that gmail overwrites the reply address in the email header. The receiver will have your gmail address as the reply address. So, the return email goes to your gmail inbox, not your original address.

This is what I got. Maybe I did something wrong or there's a workaround for this. Either case, please let me know.

-n