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I have an Exchange server 5.5 that I send mail out to the Internet, will the underscore cause any problems with older mail systems not being bale to receive mail from me and why? &nbsp;I know underscores are not RFC compliant per <a href="http://www.faqs.org/rfcs/rfc1035.html" rel="ugc">http://www.faqs.org/rfcs/rfc1035.html</a>, but I have sent mail out like this for years with no problem until now someone says they have a Groupwise mail server not receiving mail from me due to &quot;a rejection due to validation failure.&quot; &nbsp;<br />
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Although I know it is not the preferred naming convention for a mail server, will it in all intents and purposes cause mail to not be received by certain mail servers?<br />
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thanks.
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I have an Exchange server 5.5 that I send mail out to the Internet, will the underscore cause any problems with older mail systems not being bale to receive mail from me and why?  I know underscores are not RFC compliant per http://www.faqs.org/rfcs/rfc1035.html, but I have sent mail out like this for years with no problem until now someone says they have a Groupwise mail server not receiving mail from me due to "a rejection due to validation failure."  

Although I know it is not the preferred naming convention for a mail server, will it in all intents and purposes cause mail to not be received by certain mail servers?

thanks.

Underscore in Exchange server name

An email client, email reader or more formally mail user agent (MUA) is a computer program used to access and manage a user's email. A web application that provides message management, composition, and reception functions is sometimes also considered an email client, but more commonly referred to as webmail.