Replication .dovecot-sync.lock

[Hans-Werner Paulsen]

Hello all,
I have set up two servers with dovecot and replication. The mail location is
mail_location = sdbox:/var/spool/mail/%u
Everything works fine when I override the homedirectories
userdb {
  driver = passwd
  override_fields = home=/var/spool/mail/%u
}
But, when I do not override the homedirectories, replication does not work,
and the following error is logged:
Oct 24 14:40:45 dsync-local(hans): Error: Couldn't create lock /afs/mpa/home/hans/.dovecot-sync.lock: Permission denied

With a self-written module an IMAP user can get access to his homedirectory:
protocol imap {
  mail_plugins = afsToken
}
The user has to type in his password. Obviously this does not work for
replication.
Is there a way to specify a different location for the lockfile?
Isn't better to use the maildirectory but the homedirectory?
Is there a way to set the homedirectory differently for replication?

Thank you for any help.
HW

-- 
Hans-Werner Paulsen		hans at MPA-Garching.MPG.DE
MPI für Astrophysik		Tel 089-30000-2602
Karl-Schwarzschild-Str. 1	Fax 089-30000-2235	
D-85741 Garching