How to turn off Emacs's auto line wrapping for the current session? I normally need the automatic wrapping, but when editing a email draft, I don't need that. Is there a way to turn it off for a while?
Depending on which flavor of automatic line wrapping you're using, it'll be one of
if your lines wrap hard at the right-hand edge of the window, or
if your lines "soft wrap" at the whitespace nearest the right-hand edge of the window.
(If you're using an Emacs version older than 24.4, it may also be
M-x longlines-mode, if your lines wrap hard at a given column.)
If you've issued the wrong command for your configuration, then the message in the minibuffer will say "...enabled" instead of "...disabled"; in that case, just issue the same command again to re-disable the bogus mode, and try the others until you've found the one which disables the mode you're actually using.
These are buffer-local modes, so issuing the command will affect only the buffer you're in when you do so; in all other buffers, you'll still have the benefit of line wrapping unless you similarly turn off the mode there as well.
Should you wish later to turn line-wrapping back on, just reissue the command you used to disable it.