Can't send invoices using Zoho SMTP

I'm having extreme difficulty getting QuickBooks Desktop to send invoices using Zoho Mail SMTP.

I have tried the following combinations of SMTP settings in Edit > Preferences > Send Forms, but none seem to work.
- SMTP: smtppro.zoho.com, PORT: 465, SSL: yes

- SMTP: smtppro.zoho.com, PORT: 587, SSL: yes

- SMTP: smtp.zoho.com, PORT: 465, SSL: yes

- SMTP: smtp.zoho.com, PORT: 587, SSL: yes

The Zoho account doesn't have MFA enabled but I've also tried setting up an application-specific password in the Zoho Security settings. Doesn't make a difference for either the app password or account password.

When using the 465 port it hangs for a long time before prompting for "wrong password" but when using the 587 port it comes back immediately with the "wrong password" prompt.

Is Zoho blocked by QuickBooks? I am able to use these SMTP settings in Outlook desktop and can send emails just fine.