MX record in diffrent domains points to the same mail server

[Jim Reid]

>>>>> "jsayra" == jsayra  <jsayra at ssa.siemens.es> writes:

    jsayra> I want all the MX records in the three domains point to
    jsayra> the mail server in domainA.com. Something like that:

    jsayra> - db.domainA file: "domainA.com.  MX 10 mailsvr.domainA.com."
    jsayra> - db.domainB file: "domainB.com.  MX 10 mailsvr.domainA.com."  
    jsayra> - db.domainC file: "domainC.com.  MX 10 mailsvr.domainA.com."

    jsayra> Is this possible such solution?

Yes.

    jsayra> Have I to put a glue record in the db.domainB and
    jsayra> db.domainC files for the mailsvr.domainA.com record?

No. In fact you must NOT do this. First of all, glue records are only
needed for zone delegations. [ie When the master name server for .com
delegates example.com and the name servers for that delegation are
also in example.com. So the .com zone has to include A records - glue
- for ns?.example.com or whatever.] MX records do not need
glue. Secondly modern versions of BIND don't allow you to add records
that are in a different domain from the zone that is being loaded. [ie
You can't have an A record for domainA.com in the zone file for
domainB.com.  However you can have names in domainB.com as the targets
of MX, NS, CNAME, PTR, etc records in domainA.com's zone file. So an MX
record like
	domainB.com.  MX 10 mailsvr.domainA.com.
is perfectly legal in DNS terms at least. It's a different story when
mailsvr.domainA.com's mail system has not been configured to accept
mail for domainB.com.] If you try to add glue for these MX records,
the name server will scream and shout about it and ignore those records.