As it stands perdition only connects to one real-server.

If more than one real-server is supplied using the outgoing_server

option then those real servers are tried in order. Though

there is a (very simple) round-robin algorithm that selects which

one to try first.

Could you describe in a little more detail what you need to achieve

with two mailboxes? It may be possible to enhance perdition in order

to meet your needs.

As I said before, I am about to start a mass migration of thousands

accounts (pop3)

that might take a really long time.

Understood.

Before knowing Perdition, my plan was to write a pop3 proxy (have done

that in the past) that monitors if an account has been transferred or not

and points to the right server (new/old).

I have made some one-off customisations to perdition in the past
to do things like this. If you are interested I'd be happy
to talk over what something that does this in a generic way
that could be merged into the main code might look like.