Cannot send email when VPN turned on

Hi,

I have just installed Avast Ultimate and I have the following issue. I cannot send email when the VPN is turned on.

I have a bigpond email account and use the setting SMTP.telstra.com to send mail

I have changed the settings to both port 465 and 587 with SSL/TLS turned on.

As soon as I turn the VPN back on the send part of the account immediately goes offline.

When I turn the VPN off the system sends mail as normal

My system on the mac is High Sierra and I use the native mail account

Any help?