It is actually quite common for spammers to send emails from a random email address on the domain they are sending to. About all you can do is setup good anti-spam software on the exchange server, or on a mail gateway infront of the Exchange server. If you do this, you can probably setup the main gateway to reject all emails from the internet which say that they are from your domain as all emails from your domain should be coming from your Exchange server not from the internet. =========== See this similar <a href="http://itknowledgeexchange.techtarget.com/itanswers/how-to-find-and-remove-bots-from-your-network/">question and answer(s)</a>.

It is actually quite common for spammers to send emails from a random email address on the domain they are sending to. About all you can do is setup good anti-spam software on the exchange server, or on a mail gateway infront of the Exchange server. If you do this, you can probably setup the main gateway to reject all emails from the internet which say that they are from your domain as all emails from your domain should be coming from your Exchange server not from the internet. =========== See this similar <a href="http://itknowledgeexchange.techtarget.com/itanswers/how-to-find-and-remove-bots-from-your-network/">question and answer(s)</a>.