if you are getting some kind of error like this: delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused.
In your logs you can find some errors like: TROUBLE in pre_loop_hook: db_init: BDB no dbC: __fop_file_setup: Retry limit (100) exceeded, File exists. at (eval 80) line 283.
its amavis bug, you can fix it:
/etc/init.d/amavis stop
rm -rf /var/lib/amavis/db/*
/etc/init.d/amavis start
sendmail -q