iPhone 18 Pro Max displays invalid address error when sending email

Question

Level 2

173 points

iPhone 18 Pro Max displays invalid address error when sending email

I can't send emails from my iPhone 18 Pro Max with iOS 27.2. No matter what the destination email address is, I get an error message that says it is an invalid address (see screenshot).

I can send precisely the same messages to the exact same addresses from my M4 MacBook Air running Mac OS 27.2 without any issue. I never had the issue with my previous iPhone 17 Pro Max running a beta version of iOS 27 and before. The new iPhone 18 was set up from an iCloud backup of my iPhone 17 created immediately before the new phone setup, so the server settings for my originating email account precisely match the settings on my Macbook.

Any ideas what is going on?

[Edited by Moderator]

iPhone 18 Pro Max

Posted on Nov 1, 2026 7:06 AM

Reply

Answer 1

Top-ranking reply

Lawrence Finch

Community+ 2026

Level 10

244,000 points

Nov 1, 2026 7:51 AM in response to Brian Shaw3

The key message is “rejected by the server”, which is a problem at debbie’s email provider, not your iPhone.

As to why it only happens from your iPhone, it might be that the server can’t determine the sending network. And that could be because you are using VPN on your iPhone:

Do you have a 3rd party VPN installed, even if you are not using it? If so, delete the VPN profile in Settings/General/VPN & Device Management/VPN, then restart your device. Don't just turn it off; delete the profile. Updates sometimes "break" VPN, and it needs to be removed. If that fixes it, you can try reinstalling VPN, but probably shouldn't.

Reply

Answer 2

Brian Shaw3 Author

Level 2

173 points

Nov 1, 2026 10:42 AM in response to Brian Shaw3

Unfortunately, it's not Debbie's email provider (Debbie is my wife). As I said, I can send the exact same message to that exact same address from Apple Mail on my Macbook. I cannot send an email to anyone. Same error every time.

No VPN (turned off since the dawn of time).

However, I just discovered that if I send from another email account (I have another - I almost never use it - but it is hosted by the same provider, InMotion). So whatever the issue is, it has to be between my 18 Pro and InMotion and then only when using my primary account, i.e. it's not a function of any email addressee.

Reply