[vps-mail] Question about Sendmail/Spammers

[Abigail Marshall <abigail@xxxxxxxxxxxx>]

I have a question.

I have a domain on a VPS1 -- we'll call it mydomain.com

About 10 months ago, I changed mx records to VPS2, that is
named mail.mydomain.com  -- mydomain.com has been removed
from the local-host-names file on the VPS1 and I have had no
problem receiving email sent to mydomain.com

I just noticed that the messages file on the VPS1 has a
significant number of "User unknown" bounce messages for
mail to the main email addresses at mydomain.com - for
purposes of discussion we'll call it sales@xxxxxxxxxxxx

However, these look like they are coming from spammers, not
legit emailers. They have weird combinations of letters in
the return email address - fhj521@xxxxxxx or
feipo1230@xxxxxx - or come from ISPs in China.  I have never
had any complaint of mails to sales@xxxxxxxxxxxx not getting
to its intendent recipient.

So my question is - technically speaking - is there a way
that spammers get around or avoid mx records, connecting
directly with the server on the basis of host name?  I
basically want to know how this mail is getting to the
mydomain.com server in the first place. (Of course, it's
fine with me if all the spam mail bounces, but I'm still
curious, in part because I'm wondering if there is any way
legit mail could also end up coming to the mydomain.com
server - rather than being routed by MX records to
mail.mydomain.com. (NOTE: there is only ONE MX record
specified for this domain)

-Abigail



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