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We setup a spam filtering box as the first stop of incoming email of our company. &nbsp; Our outgoing emails are being handed by another exchange box. &nbsp;<br />
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The spam filtering box has a mx record on the public dns server. &nbsp;<br />
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One of our vendors is saying they cannot receive email from our domain at all. &nbsp;They told us they have put our domain name into the whitelist of their spam filter. &nbsp;<br />
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When we tried to telnet to their domain from our outgoing exchange box via port 25, connection is being rejected right the way.<br />
<br />
What could be wrong? &nbsp;Is it ourside or theirs
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We setup a spam filtering box as the first stop of incoming email of our company.   Our outgoing emails are being handed by another exchange box.  

The spam filtering box has a mx record on the public dns server.  

One of our vendors is saying they cannot receive email from our domain at all.  They told us they have put our domain name into the whitelist of their spam filter.  

When we tried to telnet to their domain from our outgoing exchange box via port 25, connection is being rejected right the way.

What could be wrong?  Is it ourside or theirs

outgoing email cannot be received.

Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

Email Protocols

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.