Many people using mutt have experienced that when you run mutt inside a screen process, mutt starts to 'paint' empty space with hard spaces which make it hard to copy-paste without also selecting those 'empty spaces'.

I have been busy looking for a solution, and asked around on the mutt-users mailinglist. There were a lot of people who experienced the same problem I have, and Thomas Dickey (Mr. Terminal God :)) mailed me the solution which, for archiving purposes, i'll quote below.

The solution: (original link)

Add or change this line in your mutt configuration:

color normal white default

Add these lines in your .screenrc configuration file:

defbce on

term screen-bce

The first enabled the 'BCE' extension, the latter tells screen to use the 'BCE-Enabled' termcap/terminfo file for its shells. You need to restart any running screensessions to activate this fix. But that don't matter much, does it?

Also read about The 'BCE' (Background Color Erase) terminal capability.