Milter-greylist

Look at the default configuration:

greylist 30m
autowhite 1d

Consider the following scenario:

1. sender@... sends an email M1 to rcpt@... at
0:00 and gets delayed by milter-greylist.

2. sender@... sends another email M2 at 0:40 and gets
accepted. The triplet (IP, sender, rcpt) is added into autowhitelist.

3. The triplet is expired at 24:40.

4. The sender's MTA resends the first email M1 at 25:00 and gets
delayed again.

5. sender@... sends yet another email M3 at 25:40 and gets
accepted. The triplet is added again into autowhitelist.

6. The triplet is expired at 49:40.

7. The sender's MTA resends the first email M1 at 50:00 and gets
delayed again.

If above scenario were repeated, the first email M1 whould not
delivered and finally bounces to the sender. Lesson: autowhitelist
should have enough long lifetime, for example 5 days.

Just FYI.