Okay, this time, "for real"?
Yet another test. With new ISP making IPv6 available, host had automagically picked that up ... but alas, sending SMTP (& notably SPF) not prepared for that ... and in any case wanted to test the IPv4, not IPv6 (oops), so ... have autoconf & accept_ra disabled for now on that interface, to be able to test via the new IPv4.
$ grep . /proc/sys/net/ipv6/conf/eth0/accept_ra /proc/sys/net/ipv6/conf/eth0/autoconf /proc/sys/net/ipv6/conf/eth0/accept_ra:0 /proc/sys/net/ipv6/conf/eth0/autoconf:0 $ tail -n 6 /etc/sysctl.conf# for now, disable autoconf and accept_ra for IPv6 on eth0 # (not yet expected for SMTP SPF, etc.) # grep . /proc/sys/net/ipv6/conf/eth0/accept_ra /proc/sys/net/ipv6/conf/eth0/autoconf net.ipv6.conf.eth0.accept_ra=0 net.ipv6.conf.eth0.autoconf=0 ######################################################################## $
From: "Michael Paoli" Michael.Paoli@cal.berkeley.edu Subject: Re: [BALUG-Test] And now IPv4 email/SMTP/lists should be originating from the new IPv4 IP Date: Tue, 17 Dec 2019 03:00:24 -0800
And yet another test ... ought be a "good" one this time. ;-) I *temporarily* disabled the IPv6 IPs - to force IPv4 (yes, there are other ways ... but for the relatively quick-and dirty ... also still testing and flushing out any minor issues that may remain in the full /etc/network/interfaces ifup/ifdown functionality).
Also, relevant SPF records updated (alas, had dropped TTLs, and queued the changes, but forgot to get 'em in earlier) ... so that part of it ought work now too (and might otherwise prevent delivery, and rightfully so - especially with -all).
From: "Michael Paoli" Michael.Paoli@cal.berkeley.edu Subject: Re: [BALUG-Test] And now IPv4 email/SMTP/lists should be originating from the new IPv4 IP Date: Sun, 15 Dec 2019 07:44:52 -0800
Drats ... didn't actually go via IPv6 ... will test more later.
From: "Michael Paoli" Michael.Paoli@cal.berkeley.edu Subject: Re: [BALUG-Test] And now IPv4 email/SMTP/lists should be originating from the new IPv4 IP Date: Sun, 15 Dec 2019 07:37:05 -0800
And one more test, with IPv6 temporarily disabled, to force IPv4 ...
From: "Michael Paoli" Michael.Paoli@cal.berkeley.edu Subject: [BALUG-Test] And now IPv4 email/SMTP/lists should be originating from the new IPv4 IP Date: Sun, 15 Dec 2019 07:11:33 -0800
And now IPv4 email/SMTP/lists should be originating from the new IPv4 IP, traffic may be via IPv4 or IPv6 (no change on the IPv6), but at least for that traffic going over IPv4 ...