Provide possible explanations for why someone's partner may respond to their email and suggest that moving on is the best course of action.
LW1 - This has been an off and on relationship for six years.  Perhaps his current girlfriend (wife?) got into his email and found your notes and she is the one who responded.  Or perhaps she found out about you and he was told to cut it off.  Or perhaps he's a jerk.  Or perhaps you don't take social cues well.  It could be so many things but the bottom line is you should take his request to heart and move on.