Unexpected Email Routing to Lower-Priority MX Record

Hi Salamat_Shah,

The short answer is yes, there are scenarios that can cause e-mail to route over less-preferred hosts (based on the priority). Some scenarios are within your control; others are not.

Rather than going through all the scenarios I can think of (and I'm sure others would be able to think of more), I'd rather bring it back to basics and give you an oversimplified starting position:

If you've gone to the trouble of publishing what is essentially a "back-up route" for mail delivery, you should also be expecting that it can and will be used periodically. What you cannot guarantee/achieve is that all mail will only be delivered over the primary route - you have to adjust your expectations there as you're not in control of how the sending system decides which host to send to.

Unless a significant volume of mail is being routed over your less-preferred mail host(s), there's likely nothing to worry about and you should not take it as a sign of misconfiguration of your environment.

Cheers,

Lain