Like when they help you with an issue do you send a last email to say thank you? I have been undecided about this because I thought it is better not to in order to save them some time opening a useless email. So I figure just not say anything more. Sometime I think they will be thinking 'oh another annoying email asking for more' so I just won't send anything when problem is solved. Other times I have. Please tell me how you deal with this important situation.