If you install McAfee VirusScan Enterprise on an Exchange Server you will find that your outbound mail is being blocked. By default McAfee only allows certain processes to send out on port 25. Exchange isn’t one of them.
The block is caused by the Access Protection component. Disabling this component entirely would allow your mail to flow again. However, disabling an entire protection component may not be ideal. Instead we list a couple of options below to allow Exchange through without sacrificing security.
Right click on the McAfee taskbar icon and select VirusScan console from the context menu.
Select Access Protection and click the Properties button.
From here select the Antivirus Standard Protection tab and remove the check mark for the line item titled Prevent mass mailing worms from sending mail. This will disable that one sub-component under Access Protection and allow outbound SMTP.
If you want to keep security tighter still, select Prevent mass mailing worms from sending mail (make sure the check mark is added back to the Block column) and click the Edit button.
In the Processes to Exclude field add the following items separated by commas; MSExchangeFrontendTransport.exe, MSExchangeTransport.exe, EdgeTransport.exe.
Click Ok to save.
After you make this change mail will flow from your server again. Any messages queued in transport will deliver on the next retry. If you added telnet to the exclusions list you will also be able to perform telnet tests over port 25.
Great article on ports required for mail flow by Microsoft.
How about you? Have you experienced this problem? Drop a comment below or come join the conversation on Twitter @SuperTekBoy.