Sending Email from Mobile devices with Wi-Fi OFF, SMTP auth failure.

Sending Email from Mobile devices with Wi-Fi OFF, SMTP auth failure.

Can not send without wifi enabled, on devices using cellular connections, ie 4G.  Devices on wifi work fine, tested on multiple domains and devices. Issue seems systemic with ZOHO. Check your change log!

550 Please turn on SMTP Authentication in your mail client. mail-ot1-f42.google.com [209.85.210.42]:40772 is not permitted to relay through this server without authentication.