Mail "send relay" issue

[Tech198]

Hi all..

Having issues sending email from iPhone internationally.

My parents are in Canada on holidays, and unable to send me email to my local ISP email account from her iPhone 5c.

Every-time she tries to, she gets a SMS relay. Cannot send.. error.

she can receive emails fine.. Both of us are with the same ISP, and have no problem from mac to mac locally.

I think she also had the same SMS relay issue occurring local to to one of her friends email in the same country...

I think these two issues are related, but why would it only happen on iPhone?


When i set her email account up, it was iMAP.

 

[Tech198]

Problem solved.

for some reason you need to authicate SMTP over 4G ... I guess its probably used to pretect abuse...

Why is this required over mobile carrier and not over Wifi ? since its still going across SMTP servers anyway....

 

[deeddawg]

Do they use the same provider for email, cellular service, and home networking?

If so the SMTP server likely recognizes the home network external IP as being within the provider's network and thus doesn't require authentication. Same for when they're on domestic cellular data, it's the carrier's network so it's trusted. Now that they're out of the country, they're roaming on an untrusted network and thus authenication is needed -- as you say to protect against abuse from SPAMmers.

 

[Tech198]

ya they use the same provider.

That's makes sense.