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Configuring rpc over http for pop users to resolve the issue.
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Configuring rpc over http for pop users to resolve the issue.

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After installing the Barracuda SPAM &amp;&nbsp;Firewall 300 all pop users are unable to send emails. &nbsp;The users receive a 550 error (domain does not exist) and in the barracuda log it's being blocked as Invalid Domain. &nbsp;If the pop users are in the office or use Outlook via RDp then they can send emails fine. &nbsp;Any ideas? &nbsp;Thanks in advance.
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After installing the Barracuda SPAM & Firewall 300 all pop users are unable to send emails.  The users receive a 550 error (domain does not exist) and in the barracuda log it's being blocked as Invalid Domain.  If the pop users are in the office or use Outlook via RDp then they can send emails fine.  Any ideas?  Thanks in advance.

Pop users unable to send emails after installing a Barracuda SPAM filter

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

Various techniques are used to prevent email spam (unsolicited bulk email). No technique is a complete solution to the spam problem, and each has trade-offs between incorrectly rejecting legitimate email (false positives) vs. not rejecting all spam (false negatives) - and the associated costs in time and effort. Anti-spam techniques can be broken into four broad categories: those that require actions by individuals, those that can be automated by email administrators, those that can be automated by email senders and those employed by researchers and law enforcement officials.