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At first sight, it seems that MX and SRV records serve the same purpose.

They both:

  • Point a client to the name of the host the server is on
  • Support prioritizing/fallback

I'm aware that MX predates SRV (RFC974 vs RFC2782), but in a modern context, MX just seems like a specialization of SRV for email.

My questions:

  • Could MX conceivably be deprecated in favor of SRV, retaining all functionality?
  • If so, is there any initiative in this direction?
  • Would there be any advantage to using SRV (besides consistency)?

After a bit of investigation, it seems that there are SMTP servers that use SRV.

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  • What is the technical problem you face that needs this question to be answered? Have you read the help center and "bad question" list? – Sven Nov 21 '14 at 11:44
  • @Sven I guess the motivating practical question is "can I simplify automatic management of my DNS records by using SRV instead of MX" but I already know that I can't, currently, so I guess you're right, this is a poor fit for ServerFault. Do you think there's a more appropriate place in StackExchange? – loopbackbee Nov 21 '14 at 12:16
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  • On a purely theoretical functional/technical level: Yes. In reality: No way. You would have to change an extreme amount of software and every MX related DNS entry. Potential gain: Effectively zero.
  • No, not that I am aware of. It's useless, so why should there be one?
  • SRV allows to specify ports. That could be a minor advantage, but since everyone has commited to the ports in use, I don't see why it would be necessary.
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1) Conceivably, from a purely technical angle: yes

2) No. The world operates with mx records and there is no incentive to change from a working solution to a different-but-functionally-identical solution.

3) The ability to direct mail for a given domain a non-standard port

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