Q:
subject: Delivery Final Failure Notice
Can not deliver the message you sent. Will not retry.
Sender: <xxx@abc.com.cn>
The following addresses had delivery problems
<KHeffley@xxx.com> Reply from mail.xxxx.yyy.com[xxx.xx.xx.xx]: 500 Line too long
<MorganMalone@xxx.com> Reply from mail.xxx.yyy.com[xxx.xx.xx.xx]: 500 Line too long
<RayMaynard@xxz.com> Reply from mail.xxx.yyy.com[xx.xx.xx.xx]: 500 Line too long
A:
The message was coming from the SMTP proxy service on the firewall. The proxy service has a setting that controls the maximum line length. This was set to 1000. To fix it I increased the limit to the one you said was imposed by Exchange of 8,000, resent my test email and it went through just fine. Just an FYI-for some reason most of the emails I was notified of came from the xxx.com domain. To fix (I have the Watchguard Firebox X Edge X20e)
1. Firewall > Incoming > SMTP Proxy
2. Click Edit
3. Click the SMTP Settings Tab
4. Change Maximum Line Length