could not read from amavisd socket /var/amavis/amavisd.sock: No error: 0

[Damian]

> Dec 26 17:03:28 batman spamd[86118]: spamd: handled cleanup of child pid [5276] due to SIGCHLD: DIED, signal 4 (0004)

spamd has been killed with signal 4 (illegal instruction). Do you have built perl for the wrong architecture? Mail::DKIM for 
example is used by both Amavis and SpamAssassin, and depends on Digest::SHA which has an XS component. What happens when you feed 
a problematic email into "spamassassin -D" on the terminal?