SMTP Error: 500 Line too long

Last reviewed on March 28, 2012   —  No comments yet

When you receive "500 Line too long" error message in an NDR, it's because the message has more than the allowed number of consecutive characters in one line (ie, no line feeds) and the SMTP server or firewall / antispam filter bounced the message.

The line limit in Exchange Server is 8000.

WatchGuard and Ironport are known to have a default of 1000 characters. Other antispam filters may have a similarly low limits.

To change it in WatchGuard, edit the SMTP properties (in WatchGuard) and set the maximum email line length higher. For the exact steps, or for other firewall/antivirus software, you'll need to review the documentation that came with your software.

About Diane Poremsky

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

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