An error occurred while sending mail: Outgoing server (SMTP) error.

ftr

Hello,

VPN blocks outgoing mails on Windows Thunderbird and lets them pass whenever I turn it off.

The error message is:

Sending of the message failed.
An error occurred while sending mail: Outgoing server (SMTP) error. The server responded: opmta1mto16aub smtp.orange.fr ****** Service refused, please try later. OFR105_103 [103].

Any help appreciated.

• ftr

Alexandru_BD

Hello,

That's almost certainly Orange blocking SMTP traffic from VPN IP addresses. Many ISPs block or rate-limit SMTP connections coming from VPN IP ranges, IPs flagged as datacenter or anonymous, or IPs outside their country, and the error code is typical of IP-based rejection, not a Thunderbird configuration issue.

The cleanest solution is to exclude Thunderbird from the VPN usign the Split Tunneling feature. This allows Thunderbird to use your normal ISP IP while everything else stays protected via VPN, and you don't have to disable the VPN entirely for the email to work properly. The second option would be to try different servers, so for example if you’re connected to another country like US, Germany, etc, switch to a server from your country, so if you are in France and you are using Orange, choose France.
However, even in this scenario it is highly possible that the SMTP servers still block the VPN IPs, but it’s worth testing.
The third option would be to change SMTP Port. Open Thunderbird and go to account settings, select outgoing server (SMTP) and make sure you're using port 587 and STARTTLS for connection security. Avoid port 25 as this is often blocked over VPN, and SSL on port 465 (sometimes restricted). Port 587 + STARTTLS is the modern standard.

I hope this helps.

Regards