Rarely emails are rejected, but today I got a bounce from AOL:
554 Message not accepted due to failed RFC compliance
What can be the reason for this? I read that some strangeness (Exotic To-field content, too many invalid/rare characters/data in the mail body) in the actual email can cause this.
How can I find out the underlying reason?
Blacklists come back negative so far for the mail server (except for one).