I have been sending to xxx.com from the past without a problem, but last week it started to act weird, I have been receiving bounced emails from xxx.com with a content:
An error occurred while trying to deliver the mail to the following recipients:
but yyy.com are receiving without a problem. Is this a phplist related problem or SES? At this point, I’m at lost. I have already checked my IP reputation but still got high scores and not even blacklisted to other sites.