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Unexpected Email Routing to Lower-Priority MX Record
We currently have two MX records configured in our public DNS:
- Primary MX Record: Priority 10 (EOP)
- Secondary MX Record: Priority 50 (retained temporarily)
Despite the lower priority (higher numerical value) of the secondary MX record, we’ve observed instances of email traffic being routed to the priority 50 record. Could you help clarify why this might occur? Specifically:
- Are there scenarios where a higher-priority MX record (10) might be bypassed in favor of a lower-priority record (50)?
- Could this indicate misconfiguration, DNS propagation delays, or server availability issues?
We aim to ensure proper email delivery to the intended priority 10 endpoint and would appreciate guidance on resolving this discrepancy.
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
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
Thank you LainRobertson
