I am currently using K-9 Mail on my Samsung Vibrant (Galaxy S) and I use squirrel mail on my computer. When using SquirrelMail I can designate a priority for outgoing emails (low, normal, high) as well as request delivery and read receipts. Is there an app that allows me to set these designations/requests?
I don't know of any apps off of the top of my head. There is Issue #4664 in Google's Android code to add that feature to the base Gmail application. (I voted for it, but it hasn't been reviewed yet.)