I installed zarafa on my vserver and use as MTA postfix. The webaccess works fine, I can revceive and send emails, also receiving mails with thunderbird (IMAP ssl/tls) works. But there is a problem, sending emails with thunderbird. I established an account in thunderbird with imap ssl/tls connection which works finde, and a starttls smtp connection on port 25 for the outgoing mail server.

If I try to send an email with thunderbird I get an error: 5.7.1 Relay access denied

this is my mail.log

Sep  7 16:10:07 postfix/smtpd[6153]: connect from p4FE06C0A.dip.t-dialin.net[79.224.110.10]
Sep  7 16:10:08 postfix/smtpd[6153]: NOQUEUE: reject: RCPT from p4FE06C0A.dip.t-dialin.net[79.224.110.10]: 554 5.7.1 <[email protected]>: Relay access denie$
Sep  7 16:10:10 postfix/smtpd[6153]: disconnect from p4FE06C0A.dip.t-dialin.net[79.224.110.10]

and this my /etc/postfix/main.conf

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

virtual_mailbox_domains = firstdomain.de, seconddomain.de
virtual_mailbox_maps = hash:/etc/postfix/virtual
virtual_alias_maps = hash:/etc/postfix/virtual
virtual_transport = lmtp:127.0.0.1:2003
myhostname = mail.firstdomain.de
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = localhost
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = ipv4

I don't know what to do, because actually sending mails to internal and external addresses works with the webaccess.

Perhaps somebody can help me?