3

I use gmail to receive e-mails both from my gmail address and my own domain, but gmail no longer allows you to send e-mails from your own domain name unless you provide your own SMTP server to send via.

Therefore I am trying to configure Postfix on an Ubuntu server to relay e-mail from any remote device to the destination e-mail address on the e-mail. I only want the server to relay e-mails from mydomain (only if authenticated) and not retain any emails on the server in user mailboxes.

Currently I been able to relay e-mails from a particular source address, however e-mails that are send to a gmail address are bounced when relayed. If I use sendmail from the server itself, gmail does not bounce it proving that gmail is happy to receive e-mails from my server. But when e-mails are relayed I get the following message from gmail:

status=bounced (host gmail-smtp-in.l.google.com[2a00:1450:400c:c00::1a] said:
550-5.7.1 [2001:41d0:a:f9a0::1      12] Our system has detected that this
550-5.7.1 message is likely unsolicited mail.
To reduce the amount of spam sent 550-5.7.1 to Gmail, this message has been
blocked. Please visit 550-5.7.1
http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for 550 5.7.1 more information. n6si25532296wjy.39
 - gsmtp (in reply to end of DATA command))

I also tried using header checks to strip all the headers that showed that the e-mail was from another client before it reached the server. But this didn't help.

Most of the information I find is about relaying all my e-mails through gmail which I don't want to do. I just the server to act as the final MTA that will send e-mails directly to the recipient's mailserver without being treated as spam.

My current postfix configuration:

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# 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

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = {@mydomain.com}
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = {@mydomain.com}, {server_hostname}, localhost
relayhost =
mynetworks = {my_ip_address} 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all

# Strip received from headers to hide original remote client address
mime_header_checks = regexp:/etc/postfix/header_checks
header_checks = regexp:/etc/postfix/header_checks
smtp_header_checks = regexp:/etc/postfix/header_checks
2

You are almost certainly running into mis-matched DNS entries. In your case using IPv6 transport, the AAAA and PTR records must match for the source address(es) of an MTA, also matching the EHLO name you are claiming to be.

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