Nie som odborník na tieto veci a ani sa na to nehrám, ale

Certificate #1 of 1 (sent by MX):
Cert VALIDATION ERROR(S): self signed certificate
So email is encrypted but the recipient domain is not verified
Cert Hostname VERIFIED (mail.n4all.sk = mail.n4all.sk)

Netuším čo s tým...

overenie si môžeš urobiť aj sám tu:

https://www.checktls.com/TestReceiver