I have been using Thunderbird for years. Always updated to the latest version. My current Thunderbird addresses are setup through Hostgator hosting and I've rarely had an issue. I recently set up a Zoho email address and added it to my Thunderbird platform so I can send and receive emails there. Problem is, when I send a test from one of my long time Thunderbird emails to the new email that goes through Zoho, it never shows up in my Thunderbird inbox. Never shows up in my Zoho inbox either. I can send from the new Zoho email to one of my established emails no problem using Thunderbird. But it doesn't work the other way around. I've checked everything I can think of--IMAP server settings, SMTP settings, added MX records, you name it. Not sure where the hang up is. Hopefully someone can help, thanks.