why does some outgoing mail constantly end up "Deferred" ?

[Jon Radel]

On 4/14/17 1:37 PM, William Dudley wrote:
> This, in /var/log/maillog:
> 
> Apr 14 13:17:52 dudley sm-mta[13944]: v3ALsCcO098060: to=<
> lemontree66 at sbcglobal.net>, delay=3+19:23:38, xdelay=00:00:00,
> mailer=esmtp, pri=16918651, relay=al-ip4-mx-vip1.prodigy.net., dsn=4.0.0,
> stat=Deferred
> Apr 14 13:17:52 dudley sm-mta[13944]: v3ALsCci098060: to=<
> markj at limerockcontractors.com>, delay=3+19:23:34, xdelay=00:00:00,
> mailer=esmtp, pri=16918660, relay=limerockcontractor...ction.outlook.com.,
> dsn=4.0.0, stat=Deferred

<snip>

> These mails sit in my queue, get retried, and are constantly "Deferred".

If they were in the queue for only a short period and then were
eventually sent, I'd suspect gr[a|e]ylisting.  If it were some obscure
little domain where the MX host had connectivity problems, well, that
would be it.

But 3+ days delay, where most of the mail is going to some Microsoft
service offering....   It's probably something else.  Unless you and/or
your ISP have broken TCP port 25 connectivity entirely....but you say
that this happens only with some mail.

The very first thing I'd do, as root, is to run

sendmail -qf -v

which will ask sendmail to run through the queues once, in the
foreground, and report in verbose mode what it thinks is happening as it
tries to send each piece of mail waiting in the queues, and probably
most usefully, what text the other side SMTP server sends to explain
what it is doing. Assuming that it doesn't just time out trying to reach
the remote server, which would also be obvious.  Most sensible servers
send at least some hints for the humans along with the response code.

After that I'd confirm that forward DNS, reverse DNS, and how your SMTP
server identifies itself (should be obvious in the verbose output),
match up sensibly, and your DNS data is accessible to the Internet at
large.  Getting that wrong makes you look way too much like some random
drive-by spammer.


-- 
--Jon Radel
jon at radel.com

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