mh-print-background-flag

mh-print-background-flag is a variable defined in `mh-e.el'.
Its value is

nil

Documentation:
*Non-nil means messages should be printed in the background.

Normally messages are printed in the foreground. If this is slow on
your system, you may elect to turn off this option to print in the
background.

WARNING: If you do this, do not delete the message until it is printed
or else the output may be truncated.

This option is not used by the commands P p or
P f.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 7.0 of the MH-E package that is part of Emacs 22.1.