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Even if you are a virtual host that resent email, you need to capture spam email otherwise, Gmail will block you.
Feb 18 14:55:52 beau postfix/smtp[31892]:
463F01A2EBD: host gmail-smtp-in.l.google.com[74.125.192.26] said: 421-4.7.28 [192.99.55.226 15]
Our system has detected an unusual rate of 421-4.7.28 unsolicited mail originating from your IP address.
To protect our 421-4.7.28 users from spam, mail sent from your IP address has been temporarily 421-4.7.28 rate limited.
Please visit 421-4.7.28 https://support.google.com/mail/?p=UnsolicitedRateLimitError
to 421 4.7.28 review our Bulk Email Senders Guidelines. k10si2978071qtp.33 - gsmtp (in reply to end of DATA command)
Check and restrictions
The check and restrictions when an email is send
telnet 192.168.0.18 25 #
Trying 192.168.0.18...
Connected to 192.168.0.18 (192.168.0.18).
Escape character is '^]'.
220 mail.example.com ESMTP Postfix # <-smtp_client_restrictions
HELO mail.example.com # <-smtp_helo_restrictions
250 mail.example.com #
MAIL FROM:<[email protected]> # <-smtp_sender_restrictions
250 2.1.0 Ok #
RCPT TO:<[email protected]> # <-smtp_recipient_restrictions
250 2.1.5 Ok #
DATA # <-smtp_data_restrictions
354 End data with <CR><LF>.<CR><LF> #
To:<[email protected]> # <-header_checks
From:<[email protected]> #
Subject:Hello world #
This is a body # <-body_checks
. #
250 2.0.0 Ok: queued as 463F01A2EBD
QUIT
221 2.0.0 Bye
Connection closed by foreign host.
smtpd_client_restrictions
The end of each list is equivalent to a PERMIT result.
smtpd_client_restrictions = permit_mynetworks, reject_unknown_client_hostname
smtp_helo_restrictions
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_non_fqdn_helo_hostname,
reject_invalid_helo_hostname,
reject_unknown_helo_hostname,
permit
where:
- postconf.5.html (default is yes)
-
- postconf.5.html - permits the known IP
- postconf.5.html - permits the authenticated user/process
- postconf.5.html - reject if the hostname is not fully qualified
- postconf.5.html - reject malformed domain name
- postconf.5.html - reject email when the HELO/EHLO hostname has neither DNS A record nor MX record
smtp_sender_restrictions
- The sender's email address should be valid
Others
greylist
Header check
Spam filter
Spf policy
2 SPF daemons exist
- policyd-spf-perl
- policyd-spf-python