I got a call from a customer telling me that our emails to his provider where blocked because we are not complying with the SMTP protocol.
Our server was added to a grey list for anti spamming.
I was told that our email server (EXCHANGE-CGN) is sending retries too quickly.
What did happen?
The provider did check their trace logs:
The remote mail server was busy and did send a busy message to our server.
Our server did then resend the email after 4 minutes.
This is, based on information of the provider, too fast.
I am told by them that The SMTP protocol says that the minimum retry time is 5 minutes.
My question is where can I check to see what the minimum retry time is in exchange.