Second server cannot send email to own domain (hosted on first server)

I don't know why, but after running a dpkg-reconfigure postfix and resetting the data, it's now routing correctly.

Just for reference purposes, here's the postconf -n (no different after the reconfigure):

Code:

# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
broken_sasl_auth_clients = yes
config_directory = /etc/postfix
home_mailbox = Maildir/
inet_interfaces = all
mailbox_command =
mailbox_size_limit = 0
mydestination = /etc/postfix/local-host-names
mydomain = $myhostname
myhostname = server2.main-domain.com
mynetworks = 127.0.0.0/8
myorigin = /etc/mailname
recipient_delimiter = +
relayhost =
smtp_tls_note_starttls_offer = yes
smtp_use_tls = yes
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain =
smtpd_sasl_security_options = noanonymous
smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem
smtpd_tls_auth_only = no
smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt
smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
tls_random_source = dev:/dev/urandom

Thanks very much for all your help and prodding Falko!

One of my favourite sayings goes something along the lines of "Google is the index to the unofficial manual for Linux" - this time the index failed me

Cheers
Ben