I use Thunderbird to access Zoho Mail via POP and SMTP. I have configured an app-specific password for Thunderbird to use. Everything is properly configured and works correctly — until I enable my VPN. I'm using a paid commercial VPN service (Mullvad).
When the VPN is enabled, both POP and SMTP fail to connect. When I try to check for new messages, Thunderbird shows this dialog:
When I try to send mail, Thunderbird shows this dialog:
Send Message Error
Sending of the message failed.
An error occurred while sending mail: Outgoing server (SMTP) error. The server responded: Your IP Address is blocked from further use.220 mx.zohomail.com SMTP Server ready February 5, 2026 6:49:45 AM PST.
This suggests the IP address Mullvad is exposing has actually been blocked by Zoho. I understand that I can open a support request to unblock IP addresses when this happens, but Mullvad assigns a different IP address every time I enable it, by design. It's not feasible to manually unblock it whenever this happens.
I am looking for a way to configure my account security to permit connections from any IP address (or a configurable range of IP addresses), bypassing the "suspicious activity" detection that triggers these IP blocks. As long as the connection is authenticated with my high-entropy app-specific password, it should be trusted implicitly.
I can't find a way to do that in the Zoho UI. Can anyone please help?