One year ago I made myself an addon to take copies and organising letter. For some reason I have been too lazy to release it. Now I have atleast uploaded a beta version of it for those of you who would like to use it.
It is a beta version, so there is a few bugs here and there.
It can be downloaded here:
www.pilus.info/files/LetterArchive_0.4.zipAnd yes, I have got 424 letters stored.
*edit*
I forgot some vital information. type /la to open the archieve.