Differences between version 7 and previous revision of SMTPBestPractises.
Other diffs: Previous Major Revision, Previous Author, or view the Annotated Edit History
| Newer page: | version 7 | Last edited on Thursday, August 5, 2004 4:17:05 pm | by PerryLorier | Revert |
| Older page: | version 6 | Last edited on Thursday, August 5, 2004 3:09:50 pm | by PerryLorier | Revert |
@@ -27,9 +27,9 @@
!!!Secondary [MX]'s
In general secondary [MX]'s have fallen out of favour in recent years as the internet is more reliable and there are techniques for keeping your primary up. (Such as load balancing [NAT]'s.). In general having a secondary is good if your connectivity is unreliable, otherwise it's a pain.
-Be aware that spammers regularly send to secondary [MX]'s directly to avoid aggressive [RBL] checks on the primary mailserver. This can be exploited by having a secondary [MX] that always returns a 400 series code (temporary failure), or is __stricter__ with it's [RBL] checks.
+Be aware that spammers regularly send to secondary [MX]'s directly to avoid aggressive [RBL] checks on the primary mailserver. This can be exploited by having a secondary [MX] that always returns a 400 series code (temporary failure), or is __stricter__ with it's [RBL] checks. Another trick is to list your primary mx again as the highest number mx (so that spammers hit that one first)
Regularly check that your backup [MX] still correctly relays, you won't notice a backup [MX] rejecting mail until the first time your primary goes down and all your mail is immediately bounced (not retried later).
