Does Yahoo mail do things differently?

My mail server can send and receive to most other mail servers, e.g., hotmail.com. But users at Yahoo get the following error when they try to send to us:

**********************************

Message from yahoo.com.
Unable to deliver message to the following address(es).

<semper@phomonastery.org>:
Sorry, I couldn't find a mail exchanger or IP address. (#5.4.4)

--- Original message follows.

Return-Path: <kayosassier@yahoo.com>
Message-ID: <20040811221013.97508.qmail@web61304.mail.yahoo.com>
Received: from [68.63.153.224] by web61304.mail.yahoo.com via HTTP;
Wed, 11 Aug 2004 15:10:13 PDT
Date: Wed, 11 Aug 2004 15:10:13 -0700 (PDT)
From: Kayo Sassier <kayosassier@yahoo.com>
Subject: from kayosassier@yahoo.com
To: semper@phomonastery.org
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="0-1165243483-1092262213=:92704"

--0-1165243483-1092262213=:92704
Content-Type: text/plain; charset=us-ascii

test

********************

I'm confused as to why Yahoo cannot find my mail server IP address whereas others can?

Bright Blessings,

Kayo

I've managed to answer my own question. Here is what I've found in case it helps anyone with the same problem:

Yes, Yahoo Mail and hotmail do things slightly differently. If I set up my mail server through my registrar as:

HOSTNAME MAILSERVERHOSTNAME MAILTYPE MXPREF
www phomonastery.org MX 10

Then both Yahoo and hotmail can send to my mail server.

But, if I use a different option at my registrar - MXE (Mail Easy) instead of MX, then Yahoo no longer can send mail to my mail server.

There is no help function at my registrar (namecheap.com), so I'm not sure what the difference is. Anyone know?

Magnolia Blessings,

Kayo