
Why does Gmail delay outgoing email? (for up to two days) - feklee
http://sites.inka.de/W1787/Google/2017-01-17+01_delayed.eml
======
Arnt
That message is short and consists of just a link to something, and one of the
addresses may be tainted by recent SPF failures. At a guess, some heuristics
may have decided to wait a little and see if that URL goes away due to abuse
complaints.

~~~
feklee
For the record, I also see delays with messages that primarily contain text,
though many or all of these messages also contain a URL somewhere.

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Piskvorrr
Welcome to the 1980s: SMTP is a best-effort, store-and-forward protocol - the
fact that 90% of e-mail is delivered, that it's delivered near-instantly and
that it's delivered directly(tm) to the destination server, now these are just
accidental properties. In reality, there's no guarantee on any of these -
there is even no guaranteed upper bound, e-mails can, in some cases, take
_weeks_ to be delivered.

TL;DR: e-mail sucks, do not depend on it.

That said, this seems to be the actual culprit: `softfail (google.com: domain
of transitioning @gmail.com does not designate
2a04:c9c7:0:1073:217:a4ff:fe3b:e77c as permitted sender)`

~~~
feklee
The `Received-SPF: softfail` header is added between mail-oi0-f43.google.com
and mail.inka.de. There is only a delay of one second.

The two day delay, however, happens on the sender's side, between the Google
SMTP servers 10.202.76.146 and mail-oi0-f43.google.com.

In general, email received from Gmail users is delayed, often for one/two
hours, rarely for a day or more.

~~~
Piskvorrr
In that case, that's e-mail working as designed. Adjusting expectations might
be in order - and perhaps adopting an alternate protocol suitable for
reliable+fast message delivery.

