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Asked: 2013-08-30 00:23:27 +0800 CST

How to control the originating IPv6 of emails sent by postfix?

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In a VPS with 2 IPv4 and 16 IPv6, I send emails with postfix. Each time, the email is sent from one of the IPs randomly

Received: from domain.com (a random IPv6 out of my 16 IPv6)

Thus, SPF fails (of course, softfail), as the originating IP is not in my DNS record. I can set a range of IP in DNS's SPF record, but how can I tell postfix to submit email from the main IP (the one I set rDNS)?

email

1 Answers

  1. There are two options available for binding smtp client to particular IPs/IPv6s (man 5 postconf):

    • smtp_bind_address
    • smtp_bind_address6

    I think they are pretty self-descriptive. Just make sure that related NICs/IPs are defined by inet_interfaces option.

    By the way, SPF records support multiple originating IP addresses per domain. Try to generate it with this SPF wizard. Just a quick example:

    domain.com. IN TXT "v=spf1 a mx a:1.2.3.4 a:1.2.3.5 a:1.2.3.6 ~all"
domain.com. IN SPF "v=spf1 a mx a:1.2.3.4 a:1.2.3.5 a:1.2.3.6 ~all"
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