Avast Mail Shield blocks Thunderbird via VPN with Split Tunnel

Avast Free Antivirus / Premium Security
1

Hi.

I use Mozilla Thunderbird as my mail client. I also use PIA VPN.

Often, I can’t receive mail in Thunderbird from my provider’s POP3-box over VPN, even when using Split Tunnel. When I disable the VPN, I can check mail. Even though Thunderbird isn’t using the VPN at all when Split Tunnel is enabled. Allowing Thunderbird to use the provider’s DNS makes no difference.

When I disable Avast Mail Shield in my latest build of Avast Free, I can receive mail just fine via Split Tunnel on VPN.

I have found, through trial and error, and a topic on this forum from 2010, that when I disable SSL scanning in geek:area, the problem disappears. But then Mail Shield is effectively not scanning my mail so that isn’t desirable.

Thunderbird has an option to test the connection to a mailserver. That test completes fine. Server found. Connection established. But the certificate that goes along with it is signed by Avast.

It seems that Avast Mail Shield, as a man in the middle, does not function correctly when using Split Tunnel on a VPN. I don’t want to disable SSL scanning for all my mail accounts. So what do I do?

Edit: note that sometimes I can receive mail behind the VPN. It seems to depend on the VPN IP I have at that moment. But even if my provider is blocking my IP, disabling Mail Shield should not make a difference. But it does! And using Split Tunnel should fix it. But it doesn’t!

2

Hello,
Since you’ve already found the hidden menu, have you tried exporting the Avast certificate into Thunderbird via the VPN (the option just below the one for disabling SSL), as explained in this FAQ?

export certif
export certif879×418 23.6 KB

2 Likes
3

Hi Chris.

I haven’t. Today, everything works normally. Next time it doesn’t Ill keep this in mind.

However, there is already an Avast certificate present in Thunderbird.

4

What I think might be happening is that Mail Shield sits in the middle, and thus Avast is the program checking for mail on behalf of Thunderbird and sending it through. Avast isn’t allowed outside of the VPN. When my ISP temporarily blocks VPN IP’s, Avast can’t access the mail server. But Split Tunneling Thunderbird does nothing because Avast hijacks and intercepts the actual mail checking. No certificate will change that.

I doubt there is a way to only have the Avast Mail Shield component excluded from VPN, but keep the rest of Avast on the VPN. It’s all or nothing, and then it’ll have to be nothing. Avast isn’t configurable enough for advanced users it seems.