It depends on your employemnt contract

HCL Notes/Domino 8.5 Forum (includes Notes Traveler)

Subject:

Many companies have employees sign contracts that say all emails, work performed using work computers are owned by the company. Once you leave the company you have no legal rights to access that information if you singed such a contract. Some companies also have contracts that relate to ideas you had whilst work for them, very hard to enforce, but many companies try.

Personally I believe Ethics come into based upon the reason you want access. If it's because you want to try and get former customers at the new company etc and need their emails, that would be unethical.

Feedback response number CTYR8R2N9M created by ~Mark Bubnitexader on 01/31/2012