[Dovecot] Set from address for sieve generated addresses, fixes #1662

data/conf/dovecot/dovecot.conf

@@ -262,6 +262,7 @@ plugin {
   quota_rule2 = Trash:storage=+100%%
   sieve = /var/vmail/sieve/%u.sieve
   sieve_plugins = sieve_imapsieve sieve_extprograms
+  sieve_vacation_send_from_recipient = yes
   # From elsewhere to Spam folder
   imapsieve_mailbox1_name = Junk
   imapsieve_mailbox1_causes = COPY