Hi list, While searching the web and perdition-users mailing list archive, I did not found the answer to this case. I encounter a little problem with libperditiondb_posix_regex . The context is simple : Perdition listening to IMAPS connections (from public network), with 3 backend IMAP servers on LAN. The configuration is quite simple too ;) : (this is running on Debian Wheezy , with Debian provided perdition package : version 1.19~rc5-1+b1) /etc/perdition/perdition.imap4s.conf _____ log_facility local5 timeout 40 imap_capability "IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES IDLE SORT QUOTA ACL ACL2=UNION STARTTLS" ssl_mode ssl_listen ssl_cert_file /etc/perdition/mtprx.stux.fr.crt ssl_key_file /etc/perdition/mtprx.stux.fr.key # M|map_library FILENAME: # Library to open that provides functions to look up the server for a # user. # M /usr/lib/libperditiondb_gdbm.so.0 #map_library /usr/lib/libperditiondb_gdbm.so.0 map_library /usr/lib/libperditiondb_posix_regex.so.0 # map_library "" # m|map_library_opt STRING: # String option for the map_library. # (default "") #m "" map_library_opt "/etc/perdition/transport.re" bind_address 0.0.0.0,[2a01:xxx:xxx:xxx:xx:xx:feef:6101] _____ /etc/perdition/transport.re _____ (.*)(a)stuxnet.org: mta.stux.fr:143 (.*)(a)contacts.stux.fr: zimbra.stux.fr:143 (.*)(a)stux.fr.eu.org: $1@publicmx.stux.fr:143 ____ For the 2 first lines on transport.re, no problem : auth is forwarded without rewriting and works well. For the last, I try to extract the first part of e-mail address to forward only this to the "publicmx" host. Perdition has been restarted after update of "transport.re" (according to documentation : regex are processed only one, while starting the daemon) But when auth is made on the backend server, the whole e-mail address is used ... (It's useful to say that the dovecot IMAP service works well on this backend). ____ May 1 17:16:41 publicmx dovecot: auth-worker(19430): Error: bsdauth(myuser(a)stux.fr.eu.org,172.18.10.61): getpwnam() failed: Operation not permitted May 1 17:16:43 publicmx dovecot: imap-login: Aborted login (auth failed, 1 attempts in 2 secs): user=&lt;myuser(a)stux.fr.eu.org&gt;rg>, method=PLAIN, rip=172.18.10.61, lip=172.18.2.25, session=<AxT4Jlj4CwCsEgo9> ____ Did I made a mistake in configuration ? My regex seems to match, but is it compliant for this use case ? Thanks for all your replies ;) . Regards, Christophe.