Timeout in DATA (postfix does not recognize dot to end message)

[arnoschaefer]

Hi,

I am experiencing strange behavior when trying to send mail from hosts in my local subnet.

When connecting from localhost, the exchange goes like this:

>telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 myhostname ESMTP Postfix (Debian/GNU)
HELO mydomain
250 myhostname
MAIL FROM:<myaddress>
250 2.1.0 Ok
RCPT TO:<somemailaddress>
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: test
From: myaddress
To: somemailaddress

Message...
.
250 2.0.0 Ok: queued as C8AE6FA97A
QUIT
221 2.0.0 Bye

so far so good. When connecting from another host in my local subnet (192.168.178.0/24), it goes like this:

>telnet mailhost 25
Trying 192.168.178.2...
Connected to 192.168.178.2.
Escape character is '^]'.
220 myhostname ESMTP Postfix (Debian/GNU)
HELO mydomain
250 myhostname
MAIL FROM:<myaddress>
250 2.1.0 Ok
RCPT TO:<somemailaddress>
250 2.1.5 Ok
DATA
354 Enter mail, end with "." on a line by itself
Subject: test
From: myaddress
To: somemailaddress

Message...
.
.
.
.

Then, after a timeout:

Connection closed by foreign host.

So, depending on whether I connect from localhost or a different machine, the DATA command is met by either

354 End data with <CR><LF>.<CR><LF>

or

354 Enter mail, end with "." on a line by itself

In the latter case, the . is not recognized as an EOM.

Any idea what might be wrong?

Postfix is 2.5.5-1.1 (Debian Lenny)

Here is my postconf -n:

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
config_directory = /etc/postfix
inet_interfaces = all
mailbox_command =
mailbox_size_limit = 0
mailbox_transport = lmtp:unix:/var/run/cyrus/socket/lmtp
mydestination = myhostname, localhost
myhostname = myhostname
mynetworks = 127.0.0.0/8 192.168.178.0/24 [::ffff:127.0.0.0]/104 [::1]/128
myorigin = /etc/mailname
readme_directory = no
recipient_delimiter = +
relayhost = myrelayhost
sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl/passwd
smtp_sasl_security_options =
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_use_tls = yes