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

[John Coutts]

In article <dsdfd8$137e$1 at sf1.isc.org>, csmith at dyndns.org says...
>
>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.
>
*************** REPLY SEPARATER ****************
Yes here is a prime example, which was a fairly important piece of business 
mail. In this case, the IP does have a reverse lookup, but the resulting name 
does not report the same "A" record. I have complained to POBox. but to no 
avail. At first they denied that they check the "A" record against the 
"PTR", but when I pressed them, they added the "or PTR and A records do not 
match" to the message. Big deal!
-------------------------------------------------------------
X-Pobox-Antispam: require_ptr/ returned deny: 204.209.35.42 has no PTR
 record, or PTR and A records do not match
X-Sift-Reason: require_ptr/ returned deny: 204.209.35.42 has no PTR record,
 or PTR and A records do not match
X-Sift-From: xxxxxxxxxx at trekescapes.com
--------------------------------------------------------------

Here is another one which is an order confirmation from Toysrus. In this case, 
there is simply no PTR record. I have informed Toysrus of the problem, and they 
politely thanked me and said they would take care of it. Months later, IBM (the 
network operator) has still not corrected the problem.
--------------------------------------------------------------
X-Pobox-Antispam: require_ptr/ returned deny: 170.224.105.33 has no PTR
 record, or PTR and A records do not match
X-Sift-Reason: require_ptr/ returned deny: 170.224.105.33 has no PTR record,
 or PTR and A records do not match
X-Sift-From: Shipments at toysrus.ca
--------------------------------------------------------------

J.A. Coutts