[Dovecot] Set imap_max_line_length = 2 M

data/conf/dovecot/dovecot.conf

@@ -318,4 +318,5 @@ service stats {
     user = vmail
   }
 }
+imap_max_line_length = 2 M
 !include_try /usr/local/etc/dovecot/extra.conf