I'm not sure if there are any addresses without numbers. I will check into that furher. Below I've included part of the header for a successful email using webmail, and below that an example of a problem one using an email client. The key must be in there somewhere...What does webmail do differently? Thanks again for your help....

Part of the header to a successful email to microplay.ca domain using webmail:

X-Apparently-To: encoregames@rogers.com via 206.190.37.189; Thu, 10 Feb 2011 14:36:08 -0800
X-YahooFilteredBulk: 207.96.250.22
Received-SPF: none (mta1012.rog.mail.sp1.yahoo.com: domain of 00749@microplay.ca does not designate permitted sender hosts)
X-YMailISG: Bz6D_TccZArZd3X6XCs8b8RhI64QCj8OTDQdRUzOKDvqrNKW
bd0F9ETuvwXgDGP72HDu6uc7gfyX7x2IBUgIbRKzVJUZjzDzkw p7eCtSOr25
8j6VtnhTY4Cii_uCCdU.gKTpoOpYrZB3zITmBAdY4kYD85mK2W nSV80G8M3C
pfAceN1.fdHhVpYV1xwX.b0j_ahV0bAeUc_NZS7XRDu0FCiTZU oPsG04PTfr
YwXJJz.Gd3m0Li9UflaLz60f.NkycqTbczezHTpCxqa0N1Yzjh _H7qG_Ssyg
EqSpOGkao8sh_ghHr08oTloBSN4FaG6PK3nxgdOIYjG_nSuaVJ iUtr1HBJHQ
2xbEvJ8Pt5ypMcl.F81g.ILeKIjRrTrOd5z3p74E2JBXmeYnr8 C3ZEtKdhjZ
sh6jXqIWc3nv7WRYdXzJ6ABq4AM4A6j_ZWMMNIxYUwt_gfKirI tA14TJJqr3
4FOovSpsOPEENpDief97SsjaqJ186iEfN68WSxe03Ko2vxejpk VVZOzE5w4h
ymo28F2InZhW1o5zq_ki585UVUs5z9EMpnS7ftZ7Rc0q4ILA_h j56RXzldTa
93A-
X-Originating-IP: [207.96.250.22]
Authentication-Results: mta1012.rog.mail.sp1.yahoo.com from=rogers.com; domainkeys=pass (ok); from=rogers.com; dkim=pass (ok)
Received: from 207.96.250.22 (EHLO mail.lesuperclub.ca) (207.96.250.22)
by mta1012.rog.mail.sp1.yahoo.com with SMTP; Thu, 10 Feb 2011 14:36:07 -0800

Part of header for problem email:

Hi. This is the qmail-send program at yahoo.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<00750@microplay.ca>:
Connected to 207.96.250.22 but connection died. Possible duplicate! (#4.4.2) I'm not going to try again; this message has been in the queue too long.

--- Below this line is a copy of the message.

Return-Path: <encoregames@rogers.com>
Received: (qmail 76431 invoked from network); 9 Feb 2011 23:35:59 -0000
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
s=s1024; d=rogers.com;
h=DKIM-Signature:Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subjectate:Message-ID:MIME-Version:Content-Type:X-Mailer:Thread-Index:Content-Language;
b=0Eh/g4kmpZ3CVHfordOLmk9LXtSK4YPK0x5dk3anaSvak5E9IQv5Q7 O9ihddF9r76rthI3qgCqpZaN5z4tku3k7RmwEnao6peCXXkJ1o mPFChW/SzeRYtP+iWSm3ZMAdMGsMbNRjDkVsIHfm16epGR6teto54SrSs 7N3CjC2NVA= ;
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rogers.com; s=s1024; t=1297294559; bh=6yP1pKJ4JbMpIYfWH5PKknlQzGucXmkpPX2UllXROuk=; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subjectate:Message-ID:MIME-Version:Content-Type:X-Mailer:Thread-Index:Content-Language; b=z4b3mnmjrE3vvHSQKpie9NVKx5eFk0qEET4/atGB5bsqFo90vofUx247NCejgWXaWBTmOzjgWbW9+nxaoUFZVO 0ro7A2VlZ9TeGOVP0sSvk/oznq5b0IY+yD2GQ9TzmSkV/M/pv4kKGRCo/OozUkX0rcYE7vGwIEvSACHV4zPak=
Received: from BrianInthofPC (encoregames@99.254.168.226 with login)
by smtp107.rog.mail.re2.yahoo.com with SMTP; 09 Feb 2011 15:35:56 -0800 PST
X-Yahoo-SMTP: cfGCsk2swBCPx347qTCdvaZ5FeTQjjnNMd_iC9TrxoLeJpI-
X-YMail-OSG: 7OkBWpsVM1n_8jIKTsr7wvWbZyhvbPeDtIBGVdJ5nbIPRfN
CaJX.JCIoPwhcFCmKG9MxW6Wpxuo1zfvoiEKtol2772CbfG5Ap q.k2A60VIO
h4ZAhnvcpyDrqQTQt3xGXa2ZVl7mjzTDmqRtU4tFegMiVh8TlW ylUWcK_1hn
.Zj2k6Kf1PUEOwzSmCjJOiU73URwE88txGLCdwD92s3J9eU6iQ ZpfmLibc8F
aV7w4gT20JQ--
X-Yahoo-Newman-Property: ymail-3
From: "Encore Games \(Microplay\)" <encoregames@rogers.com>
To: "'Microplay Kitchener'" <00750@microplay.ca>
Subject: test
Date: Wed, 9 Feb 2011 18:35:54 -0500
Message-ID: <000001cbc8b2$1872ed30$4958c790$@com>
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_0001_01CBC888.2F9CE530"
X-Mailer: Microsoft Office Outlook 12.0
Thread-Index: AcvIshgdQC/mLmF+SxafYx1uM+99VQ==
Content-Language: en-ca

This is a multi-part message in MIME format.

------=_NextPart_000_0001_01CBC888.2F9CE530
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit