Amavisd issue

I've a strange issue with amavisd
When i recive a bulk amount of email, amavis stop working with the following message

Code:

Jun 18 12:42:35 ns1 amavis[26265]: (26265-03) (!)TempDir removal: tempdir is to be PRESERVED: /var/lib/amavis/tmp/amavis-20150618T123958-26265-jKDjwylP
Jun 18 12:42:35 ns1 amavis[26264]: (26264-06) (!)TempDir removal: tempdir is to be PRESERVED: /var/lib/amavis/tmp/amavis-20150618T124004-26264-5GqQWtoo

I've no idea why, after that the delivery of mail stop working.
If i'll restart amavis, the flow start working again, but if i'll do a postfix flush as soon as the mailque will be processed, amavis exit again.

Any idea?

p.s.: no RAM, disk, CPu problem or similar

 

All seems ok...