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Let's say I have several domains. bossguy.com is the domain that hosts my mail (IMAP server) and where I ssh in to manage other domains, for example:

  • domain1.com
  • domain2.com
  • domain3.com

It makes sense to set up MX records for domain1/2/3.com to point to bossguy.com, so if someone emails me at whoever@domain2.com, it gets routed to bossguy.com for storage. But does bossguy.com need its own MX record (for emails sent to whoever@bossguy.com)? Currently I have it set up like this:

bossguy.com.     86400 IN MX 10 mail.bossguy.com.
bossguy.com      86400 IN A     23.xx.xx.xx
mail.bossguy.me. 86400 IN A     23.xx.xx.xx

Is the MX record needed in this case?

Also, assume all these domains share the same IP address. Then really, they could all just have MX records that equal the domain/host (domain1.com's MX being domain1.com), and it doesn't really matter since they all share the same IP. Correct?

CaptSaltyJack
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2 Answers2

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If you send mall to example. com, and that name has an IP address but no MX, the sender has to ask twice (once for MX, which fails; again for A). It works, but adding the MX record is done as a courtesy to senders.

vonbrand
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If you're receiving mail addressed to foo@bossguy.com, then yes, this domain needs MX records of its own. If this is not the case, then they are not needed.

EEAA
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  • Hmm. But technically if someone emails a host that has no MX record, it will attempt to just deliver right to that host, correct? In other words, MX records are only necessary if you want a *different* host to handle incoming mail. – CaptSaltyJack Feb 13 '14 at 02:01
  • Also, assume all these domains share the same IP address. Then really, they could all just have MX records that match (domain1.com's MX being mail.domain1.com), and it doesn't really matter since they all share the same IP. Correct? – CaptSaltyJack Feb 13 '14 at 02:09
  • @CaptSaltyJack, yes. You don't strictly need an MX record because MTAs will fallback to the A record, but that's not best practice and not all MTAs will use that fallback behavior. Best practice is to always put in an MX record if SMTP is in use. – milli Feb 13 '14 at 18:31