iCloud+ Mail sending mystery

[eN0ch]

Background: I'm a hobbyist rather than being IT trained. But I just enjoy tinkering under the hood with macs and i-devices. My latest project has been running a postfix smtp server on my iMac and relaying email through it from several devices through our local network.

Now here's my puzzle: When sending email from my iCloud+ mail account on my iPhone, it becomes clear from checking mail headers and the postfix mail log that none of these emails have passed through my server. Neither have they passed through the SMTP relay service (smtp2go), which is where the local server sends them. In fact they've gone through iCloud servers only. This is despite the fact that I've turned off the (Primary) iCloud outgoing server, leaving only one outgoing server active, that being my local postfix server. This doesn't happen when sending from our (mac) computers; only the iPhone.

Does anyone outside of the inner sanctum of Apple engineering really know how iCloud mail operates, particularly through iOS? I'm wondering if it's some hidden security protocol.

Alternatively, maybe there's something in my postfix configuration that blocks the phone but not the computers? But that seems unlikely considering there's never even a hint of postfix having received a connection request from the phone.

Thoughts, anyone?

 

[eN0ch]

Well in case anyone happens upon this post, here's the solution I found:

My suspicions were on the right track. It seems to be an issue with the way Apple has scripted the creation of an iCloud email account on iOS (when you go the easy way, selecting iCloud as the type of account). It does seem to lock a lot things in.

So the solution was to create a second instance of the same account manually (using the generic roll-your-own email config), and then with bated breath 😰 to disable "Use on this Phone" in the iCloud mail settings in the AppleID section.

Now my smtp is doing what I want with my server. Or at least it works in Mail. Spark seems to be another matter. And so to the next project ... Happy Christmas one and all 🎄🙏

 

[ManuCH]

Nice find, and I had indeed noticed the same thing. But careful: if you use your own SMTP server to send emails with your @icloud.com sender address, it will not pass the SPF check, so it's more likely to land in the recipient's spam folder.

 

[eN0ch]

it will not pass the SPF check, so it's more likely to land in the recipient's spam folder.

Appreciate the concern, and duly noted. Shouldn't be a problem as I have the server configured to relay ALL outgoing through smtp2go. That way my emails get to piggy-back on smtp2go's SPF, DKIM etc. It's working well.