This has happened before. I contacted Zoho and it seemed to work, but now my emails are not sending or taking a long time to send and half the time attachments don't attach. It just keeps saying Sending... and I have to keep clicking it to make it send. 

With the Mail app, it won't allow me to select and attach documents either.

Are these known issues?

I have my email hosted with Crazy Domains. I've been having issues with them and now they are trying to upsell me to another email plan, so it could be an issue with them. Anyone running CD email through Zoho?