I am looking for an e-mail server that can replicate the gmail plus addressing, however I would like to be able to replace the + with another character (_ or -) due to some plus haters

I would prefer a free solution that works on Linux, however I would be open to windows (server) and paid* solutions as well.

I would also add the requirements of IMAP and secure connections, but I hope that those are standard for any e-mail server by now.

*Paid solutions should be less than $50/yr, since at that price I would simply go to Google Apps and configure it like this