The recent update to dovecot-2.2.16-r1 does not work with dovecot-antispam-2.0_pre20130429: May 04 00:13:24 [dovecot] imap(xxxxxx): Error: Couldn't load required plugin /usr/lib64/dovecot/lib90_antispam_plugin.so: Module is for different ABI version 2.2.ABIv13(2.2.13) (we have 2.2.ABIv16(2.2.16))
Each time dovecot version increases, you need to recompile plugins to have them work.
Can rebuild be forced by portage?
Thanks for the hint, Brian!