Recipients Not Receiving Mail

Recipients Not Receiving Mail

When using sending mail with Zoho Mail through my web browser on my PC, the emails send fine and the recipients receive them. But when sending mail from my android device using exchange active sync, the recipient never receives the email although the emails show sent in the Sent folder on both devices with no errors and no bounce backs.

We are mostly mobile, so it's really important to be able to send and reply to emails. Thanks in advance!