113      iPhone_iPad_Mac_apple

iCloud validation of Message

I'm the maintainer of a popular PHP email sending library (PHPMailer) used on millions of web sites (e.g. it's used by Wordpress). I have had reports of a problem with some messages sent from scripts being successfully accepted by iCloud, but never appearing in inbox or junk folders, and never being bounced, i.e. they are being blackholed by iCloud. I have been able to reproduce this problem very easily.

This is not reasonable behaviour. If there is a problem with a submitted message (e.g. message format, header validation, SPF failure, spam filtering, DMARC), it should either reject or defer immediately (appropriate for a problem that's verifiable locally), or send a bounce later on.

If I send to and from exactly the same addresses and same server but using Apple Mail, the message arrives successfully.