On Sun, Oct 13, 2019 at 10:44:05AM -0700, mbridgett wrote:
> I have a problem at the moment, specifically with Epic Games - who are
> claiming that they are sending me password reset emails - but I am never
> receiving them.
>
> I SUSPECT that some outbound mail servers may be doing some kind of check
> (possibly a reverse DNS lookup - and of course my IP address resolves back
> to my ISP hostname and not "my" domain as shown below:
No, reverse DNS checks by the *sender* of email are not plausible.
However, there are few other potential sources of trouble:
.COM nameservers (MX query, referral):
byteplayer.com. IN NS ns2.123-reg.co.uk.
byteplayer.com. IN NS ns.123-reg.co.uk.
123-reg.co.uk nameservers (MX query, zone apex alias):
byteplayer.com. IN CNAME byteplayer.dyndns.org.
[ This could give some not-so-robust DNS clients indigestion ]
dyndns.org (MX query, NODATA):
dyndns.org. IN SOA ns1.dyndns.org. hostmas...@dyndns.org. 2820016809
600 300 604800 600
[ Some broken SMTP senders could require MX records ]
dyndns.org (A query):
byteplayer.dyndns.org. IN A 5.68.116.33
dyndns.org (AAAA query):
byteplayer.dyndns.org. IN AAAA 2a02:c7f:642c:6600::1
[ Some SMTP senders could try to only use IPv6 ]
$ posttls-finger -o inet_protocols=ipv4 -l none byteplayer.com
posttls-finger: Connected to byteplayer.com[5.68.116.33]:25
posttls-finger: < 220-mail.byteplayer.com ESMTP Postfix
<...multi-second greet pause on first connection...>
posttls-finger: < 220 mail.byteplayer.com ESMTP Postfix
posttls-finger: > EHLO straasha.imrryr.org
posttls-finger: < 250-mail.byteplayer.com
posttls-finger: < 250-PIPELINING
posttls-finger: < 250-SIZE 50000000
posttls-finger: < 250-ETRN
posttls-finger: < 250-STARTTLS
posttls-finger: < 250-ENHANCEDSTATUSCODES
posttls-finger: < 250-8BITMIME
posttls-finger: < 250-SMTPUTF8
posttls-finger: < 250 CHUNKING
posttls-finger: > QUIT
posttls-finger: < 221 2.0.0 Bye
[ Some SMTP senders might give up too quickly, and not get past
your postscreen greet pause. ]
$ posttls-finger -o inet_protocols=ipv6 -l may byteplayer.com
posttls-finger: Failed to establish session to byteplayer.com via
byteplayer.com:
connect to byteplayer.com[2a02:c7f:642c:6600::1]:25: Operation timed out
[ You have an IPv6 address, but no SMTP server there,
that could be a problem. ]
--
Viktor.
