disable anti-spam service cause local delivery suspended

[tiger2000]

Dear all,

i've read several similar posts on the forum and found sometimes (not always) when anti-spam service is disabled, it will cause the MTA delivery failed.

but i'm kinda of confused, cause i do have two systems(both 6.0.12 OSE) , in first system, anti-spam and anti-virus are disabled, never saw the local delivery suspended issue. but the second one does have the problem. and then enable the anti-spam service in second system solved the issue.

could someone give more details on this?

Why anti-spam (or maybe anti-virus together) should be enabled to avoid the local delivery suspended issue?
we found most enterprises already have other commercial anti-spam equipment, e.g. ironport for spam blocking, and then most of them will disable the zimbra's anti-spam service.

any advice ? Thanks.