You are right. After some RFC research Imail is not correctly following the
RFC since a MX record is present it still attempts deilivery to A.
http://www.faqs.org/rfcs/rfc2821.html
5. Address Resolution and Mail Handling
Once an SMTP client lexically identifies a domain to which mail will
be delivered for processing (as described in sections 3.6 and 3.7), a
DNS lookup MUST be performed to resolve the domain name [22]. The
names are expected to be fully-qualified domain names (FQDNs):
mechanisms for inferring FQDNs from partial names or local aliases
are outside of this specification and, due to a history of problems,
are generally discouraged. The lookup first attempts to locate an MX
record associated with the name. If a CNAME record is found instead,
the resulting name is processed as if it were the initial name. If
no MX records are found, but an A RR is found, the A RR is treated as
if it was associated with an implicit MX RR, with a preference of 0,
pointing to that host. If one or more MX RRs are found for a given
name, SMTP systems MUST NOT utilize any A RRs associated with that
name unless they are located using the MX RRs; the "implicit MX" rule
above applies only if there are no MX records present. If MX records
are present, but none of them are usable, this situation MUST be
reported as an error.
> R. Scott Perry wrote:
> > >Is there any reason why Imail will try to deliver to the A record of a
> > >domain if it fails to connect to the MX record? Can you disable it?
> >
> > The RFC requires that IMail do that. I don't believe it can be
disabled.
>
> Are you sure about this?
>
> My reading is that using 'A' records is only permissible when there
> are no 'MX' records.
>
> To quote from RFC2821:
> If one or more MX RRs are found for a given
> name, SMTP systems MUST NOT utilize any A RRs associated with that
> name unless they are located using the MX RRs; the "implicit MX" rule
> above applies only if there are no MX records present. If MX records
> are present, but none of them are usable, this situation MUST be
> reported as an error.
>
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