Most external mail providers allow for automatic forwarding of mail you received in the account they created for you (without putting the "FWD: " in front of the message title) to another external mail host. At least that has been my experience with external mail hosts so far.
If this is the case for you, you could forward it to a gmail account associated with your wife and let their SPAM filters do the work. These are quite decent. Your wife then only needs to pick up mail from the google mail account with the client she already has on her android device. This would be one of the easiest solutions, which won't be too taxing on the training part either.
On the other end of that scale is running your own mail server. This is what I do myself, using the Linux-based PostFix with the spam filter software that comes with it. But there are good Windows-based mail servers too. To my knowledge the open source hMail server
has been favorably mentioned here several times by experienced Windows system administrators on this forum alone. Having no experience with this particular mail server software, I still think it is safe to assume that you can get additional spam filter software for it if the already available SPAM filters prove to be inadequate for your own situation.
Running your own server means you have a lot more power regarding mail...but with great power comes great responsibility, so be prepared if you choose that road.