feedmail-display-full-frame

feedmail-display-full-frame is a variable defined in `feedmail.el'.
Its value is

queued

Documentation:
If non-nil, show prepped messages in a full frame.
If nil, the prepped message will be shown, for confirmation or
otherwise, in some window in the current frame without resizing
anything. That may or may not display enough of the message to
distinguish it from others. If set to the symbol 'queued, take
this action only when running the queue. If set to the symbol
'immediate, take this action only when sending immediately. For
any other non-nil value, take the action in both cases. Even if
you're not confirming the sending of immediate or queued messages,
it can still be interesting to see a lot about them as they are
shuttled robotically onward.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.