''I have two feelings about the people who still do those kinds of closings on E-mail,'' Mrs. Martin said. ''Oh, the poor, sweet dears, they still think it's a letter and they're still using the correct form of a letter.'' The other feeling is not quite as kindly: ''Aha, they think they can get away without writing a letter in a formal situation. Well, they can't.''

Some of the most creative ta-ta's emerge from close family bonds.

''My 12-year-old niece and I have developed our own little sign-offs,'' Karin Rex, owner of Computerease, a computer training and technical writing company in the Philadelphia suburbs, wrote via E-mail. ''This started as a joke between us because she -- in all her 12-year-old techno-wizardry -- was always sending me messages with computer acronyms that I could not understand. So I started to make some up with her. One of our favorites was 'EHLTB' (Elvis has left the building), which we would save as our last message.''

Kelly Keydel, a Seattle financial analyst whose husband, Kurt, works on a fishing boat in Alaska, shares a special sign-off with him when he's at sea: FYI, which stands for ''forever you and I.''

Among people who see each other regularly, sign-offs tend to be shorter, if they appear at all.

''It's people you see every day, that you have the most contact with, that you have the least amount of sign-off for,'' said Gregory Ward, a linguistics professor at Northwestern University. ''It's like in an office, you don't say 'bye' or 'see you later' or 'take care,' because those close off the interaction much more than is appropriate.''

''Best'' and its cousins albest, all my very best, all bests and best of the best are, in general, highly regarded. Jack Jackson, who used to work at the U.P.I. wire service, recalled: ''We commonly ended notes with 'bests' -- a shorthand for 'best regards.' I also recall combining sign-offs, as in 'chrs et rgds,' '' he wrote via E-mail.

But Collin Earnst of the Boston office of IXL Inc., an Internet services company, thinks 'best' is the worst. ''When someone signs their E-mail 'Best' it drives me nuts. Best what? They don't have time to write the second word? 'Best regards?' 'Best be going now?' '' he said in an E-mail note.

E-mail sign-offs can be too friendly, sometimes inadvertently.

''One time I held the wrong key down instead of Command X, which would usually insert a signature,'' wrote Rachel Hernandez, a doctoral student at a molecular genetics lab at the University of Washington. 'I held Shift X. There was a delay in the computer, so just as I pressed Send, the XXXX appeared after my name. I haven't heard from that scientist again.''