I've nothing profound to say about this topic, but I just wanted to do my bit about:
- getting it onto people's radar;
- publicising it so Adobe might be more likely to do something about it.
Cfmail mailsent logs mail as successfully sent but the receiving server has no record of the connection attempt. Happens to about 1% of messages sent.
Now I suspect anyone who has ever used <cfmail> has had this happen to them: it works reasonably well most of the time, but every now and then mail messages just vanish. They seem to spool OK - ie: they leave the cfusion\Mail\Spool directory and do not end up in the cfusion\Mail\Undelivr, and are logged on ColdFusion's end as "sent" - but the receiving mail server has no record of the message ever arriving to be sent. This has been on my radar for almost as long as I can remember, so back to at least CFMX7 (I've been using CF since 4.5, but I have no firm recollection of this sort of thing prior to CFMX7).
Issues like this are tricky to troubleshoot because they're transient, and also the involve quite a few moving parts: CFML, the ColdFusion mail spooler, a connection to an SMTP server, the SMTP server itself, and then the outbound connection from said server.
That said, there is definitely a problem here, so I think the Adobe dudes need to hunker down and start looking and not stop looking until they find the problem. This is not one of these issues wherein one looks for a certain amount of time, and then not having found anything declare "cannot replicate". If you cannot replicate, you've not finished trying. Bugs like this suck, but they are the reality of software development.
So, anyway... if you didn't know there was a long-standing transient glitch here, and were bemused by why emails go AWOL every now and then: now you know. And even if you already knew... here's your chance to do your community-spirited thing: go vote for 3312296. From there, people on the ColdFusion 11 pre-release can help Adobe track the issue down.
I'm gonna post the results of that wee Railo-usage survey that I posted the other day shortly (if you haven't done it, please do!), but I figured this was more important.