i know mailing lists should only deal with small amounts but one customer had problems with their mailing list which they had to rebuild since it was not in the export from kloxo before importing into kloxo-mr
problem they had was:
ezmlm-reject: fatal: Sorry, I don't accept messages larger than 30000 bytes
midterm solution:
modify /etc/ezmlm/ezmlmrc and change 30000 to your liking
final solution should be in the control panel to modify this