Which, despite the "VSRE," would probably still come across as douchey. I don't think the op's idea would actually even work in practice, because the recipient

Which, despite the "VSRE," would probably still come across as douchey. I don't think the op's idea would actually even work in practice, because the recipient still isn't communicating that what they are saying is polite. For all the sender knows, they could still be saying it gruffly. Smilies can accomplish what the author intended. "Can't, busy this week" Becomes "Can't, busy this week :(" If you don't mind looking like a wuss.