Stuff just happens
Today, I found another example of something I hate. Nothing bugs me more than finding a problem that should have been an issue all along, but things were working fine until for no particular reason, the problem shows it ugly little head. Specifically, today, I discovered that certain messages sent to our domain (at work), were being bounced with a 552 error code (Exceeded storage allocation). I found this particularly frustrating since I know we don’t set any specific size limits, other than a global limit of 10-15MB. The spam server is an SMTP proxy and we use watchguard fireboxes with an SMTP Proxy. I did some searching online and found that there may be an issue with the watchguard firebox in relation to an RFC for SMTP:
The RFC for SMTP explicitly states that the length of a single unterminated line can be no more than 1000 bytes. Sometimes email is rejected at the firewall for this reason because by default it will drop the connection when an unterminated line length exceeds 1000 bytes.
So now it appears the culprit for the issue is our firebox, which boggles my mind, because we’ve used it forever and just recently started having this problem. I hate when stuff just breaks for no particular reason and has worked in the past just fine for years. I am also checking our our spam software support team, to make sure their software when acting as an SMTP proxy, won’t be vulnerable to the same type of thing. Hopefully there is an easy fix for our firebox and we won’t have any more trouble. I’ve read several other newsgroup posts that indicate the firebox as the cause of the problem. Although the actual cause is some mis-configuration of the senders mail system, (typically), the firebox is doing the disconnecting.