/etc/postfix/main.cf

# These are all default Postfix settings that we won't change
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
append_dot_mydomain = no
biff = no
broken_sasl_auth_clients = yes
inet_interfaces = all
mailbox_command = /usr/lib/dovecot/deliver -c /etc/dovecot/conf.d/01-mail-stack-delivery.conf -m "${EXTENSION}"
mailbox_size_limit = 0
myorigin = /etc/mailname
readme_directory = no
recipient_delimiter = +
relayhost =
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_path = private/dovecot-auth
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_type = dovecot
smtpd_tls_auth_only = yes
smtpd_tls_received_header = yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
tls_random_source = dev:/dev/urandom

## Settings below this line are things we're modifying or adding

## Your mail server identity options
myhostname = mail.example.com
mydestination =  mail.example.com, example.com, localhost.de, localhost
mynetworks = 127.0.0.0/8 192.168.91.0/24 [::ffff:127.0.0.0]/104 [::1]/128

## Customized smtpd paramters
smtpd_banner = $myhostname ESMTP
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks, reject_non_fqdn_helo_hostname, reject_invalid_helo_hostname, reject_unknown_helo_hostname, permit
smtpd_recipient_restrictions = reject_unknown_client_hostname, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, reject_invalid_hostname, reject_non_fqdn_sender
smtpd_sender_restrictions = reject_unknown_sender_domain, reject_sender_login_mismatch
smtpd_sender_login_maps = $virtual_mailbox_maps

## Dealing with rejection: use permanent 550 errors to stop retries
unknown_address_reject_code = 550
unknown_hostname_reject_code = 550
unknown_client_reject_code = 550

## customized TLS parameters
smtpd_tls_ask_ccert = yes
smtpd_tls_cert_file = /etc/ssl/certs/ssl_main.crt
smtpd_tls_key_file = /etc/ssl/private/ssh_main_insecure
smtpd_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
smtpd_tls_ciphers = high
smtpd_tls_loglevel = 1
smtpd_tls_security_level = may
smtpd_tls_session_cache_timeout = 3600s

## Customized Dovecot and virtual user-specific settings
canonical_maps = hash:/etc/postfix/canonical
home_mailbox = Maildir/
message_size_limit = 104857600
virtual_alias_maps = hash:/etc/postfix/virtual
virtual_mailbox_domains = hash:/etc/postfix/virtual-mailbox-domains
virtual_mailbox_maps = hash:/etc/postfix/virtual-mailbox-users
virtual_transport = dovecot

## This setting will generate an error if you restart Postfix before
## adding the appropriate service definition in master.cf, so make
## sure to get that taken care of!
dovecot_destination_recipient_limit = 1

# Customized milter settings
milter_default_action = accept
milter_connect_macros = j {daemon_name} v {if_name} _
non_smtpd_milters = $smtpd_milters
smtpd_milters = unix:/spamass/spamass.sock unix:/clamav/clamav-milter.ctl unix:/opendkim/opendkim.sock

## Other customized mail server settings
default_destination_concurrency_limit = 5
disable_vrfy_command = yes
relay_destination_concurrency_limit = 1
smtp_tls_note_starttls_offer = yes
smtp_tls_security_level = may

# addeded by marcel 10.10.2014
virtual_minimum_uid = 100
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000