Messages are sent via the wrong purple accounts

I added two jabber accounts via the prpl backend and I noticed that messages are sent via the wrong one, the wrong server replied with a server message that the target recipient is invalid.

I started the chat with that user before adding the 2nd account, maybe this is related?

Start by reproducing the issue with two Jabber accounts added through the prpl backend, including a chat created before the second account was added. Trace how the existing chat selects its sending account and verify that messages use the intended account rather than the one whose server rejects the recipient.

Written by the indexing model from the issue text.