Sending email failed: Failed to transport message. Network unreachable

Hello all,

I keep getting this error when I'm trying to send emails. I've got this in
the past and I've resolved it by: completely removing akonadi, KMail,
Kontact and all their files. Basically a clean start, and about 3 reboots

I just got the error again, and I don't intend to go through all that again.

My setup is:

Fedora 31 KDE in a VMWare Fusion VM on a Mac (please don't ask why). The
Mac connects to various VPNs with various clients. The error manifests with
the clients enable or disabled.

Both accounts that I'm getting the error are GMail accounts with MFA
enabled and using an app password to login. I'm using PLAIN authentication.

I can receive emails and read them just fine. They are marked as read and
deleted on the server just like locally. So just sending is a problem,
again.

Any advice on what I should do? I'm not sure what causes this behaviour or
how to reproduce it, since I don't have this issue on another machine where
I have Fedora 31 KDE directly on the machine (no VM).

Regards,
Ovidiu