Do you have any friends or family members who would be willing to take her in for a few years until your return? I know that's a lot to ask of someone when you will be gone for several years, but it never hurts to ask people! If that's not an option, try to find a boxer rescue in your area and surrender your dog to them. That's the best way to find a good home for her. Rescues carefully screen all applicants before adoptions take place, and they provide follow-up to make sure that the new home is a good match. It's possible that your nearest rescue will be full and won't be able to take your dog in themselves right now, but they will probably still offer you support in what you need to look for in a new home - if they can't take your dog, ask them if they will give you a copy of the form they use for home visits, the application form, and a sample contract. Those items will give you a good idea of what to look for in a potential home and will help you you ask all the right questions before sending your girl home with someone else.
If your girl is not spayed yet, please do that before you start looking for a new home for her. I know you wouldn't want someone taking her just to turn her into a breeding machine. (And a rescue group would require that she be spayed before they could take her anyway.)
