dep wrote:

>> 127.0.0.1 = localhost
> 
> so kmail assumes this?
> 
>> Could it be that on those ports the protonmail bridge is communicated
>> with?!
> 
> i rather figured as much -- it was 127.0.0.1 i was most puzzled about.

kmail does not assume anything. It uses a configuration file, where you
provide the host and the port.
In the case/example you provide 127.0.0.1, which is always the localhost
address. It means that proton bridge is using a server to listen to this IP
and port. So in theory it should work if you configure your kmail account
like in the example.
The two different ports are for sending and receiving. I assume the bridge
is making all the enc/deryption transparent to whatever mail client you
use.

regards