Do I really need an MX record? (for e-mail to work)

Christian Smith csmith at
Tue Feb 7 04:13:53 UTC 2006

In article <ds84bc$he2$1 at>,
 administrator at (John Coutts) wrote:

> In theory you are correct. In the fight against spam however, many mail 
> servers 
> do fail on an "A" record check (for example my own mail provider at 
> There are some that even go so far as to reject mail if the sending domain is 
> not prepared to accept responding email by advertising an "MX" record. It may 
> not be accordong to RFCs, but it is a fact of life in todays email system.

Pobox fails to deliver to domain which have only an A record and no MX 
record or it refuses to accept mail from such domains?

I find that hard to believe in either case since Pobox purports to be a 
well run mail service.

> Again, theory and practice diverge here. I don't necessarily agree with the 
> practice, but some mail servers do a reverse lookup on the sending IP, and if 
> it contains "DSL" (or other commonly used conventions) in the name, it is 
> rejected. It is not a common practice, but it is being done.

So I've heard. I wonder if this impacts domains which contain the string 
'dsl' as part of their domain, such as

Of course, if you have a static IP address being provided by your ISP, 
you should be able to have the reverse DNS customized.

> One practice that I completely disagree with is that of rejecting mail if the 
> "A" record does not match the "PTR" record. Checking for the existence of a 
> "PTR" record is a questionable practice, but requiring it to match the "A" 
> record is pushing things a bit too far. The domain owner does not necessarily 
> have control over his/her own "PTR" record, and ISPs in general do not do a 
> very good job of maintaining these records.

Can you provide an example of a domain which blocks mail simply because 
the PTR record does not match the name of the mail server? (Setting one 
up yourself to provide as an example doesn't count) And how exactly do 
these domains determine the A record? Do they base this on name provided 
in the HELO command?

Christian Smith
Dynamic Network Services, Inc.

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