Is it acceptable to use texting spelling in regular emails?

This is a cartoon by Mike Luckovich published May 31, 2009 in the NY Times. It raises an interesting question. To what extent is it acceptable to use text type language spelling and abbreviations in emails? In about 1995 a former President of Assiniboine College told me that emails were meant to be quick communications in which the sender was not to worry about proofreading them. Misspellings and inaccurate punctuation were acceptable. Well I guess that really did not catch on! But given where things have gone, and as the Gen Yers get more into the mainstream, can we all relax and just use whatever method it takes to get our message across?