I have a question about the nature of SMTP. I have a mail exchange server I am responsible for. At present I have one MX record pointing directly to the mail exchange server. This all works fine.
I've read the RFC for SMTP, and from what I can gather, if my server goes down and mail cannot be accepted, the SMTP client trying to deliver the mail should retry at set interval, and retry for a period of time (generally 3-4 days) until either a successful delivery of the mail has been made or a permanent failure occurs (in which case it is obliged to send a report to the returnpath address?,
It is section 18.104.22.168 Sending Strategy in RFC 2821 that specifies that if an SMTP Client accepts responsibility to deliver a message to destination then it has to attempt to deliver more than once and only fail after a reasonable amount of time.
The reason I ask is because if this is true, if the SMTP server goes down, that means I will have at least 2-3 days to get it back up without any loss of service, and I don't need a backup SMTP server listed in my MX details?
If anyone knows what I'm talking about, would really appreciate a response,