I don't use 1and1, so I don't know if this is possible, but why not:
1) change current password to some stupid password
2) give password
3) reset password back to my normal password
4) move on with life
1) change current password to some stupid password
2) give password
3) reset password back to my normal password
4) move on with life
So, he should give them his password, but he should then change it.