search mailreader to read big archives

Who hat experiences with mailreaders? - I want to copy
some of my big mail archives (each files about 8MB 
with about 5.000 Mails)   to Z. and read them 
when I'm travelling. The mailreader delivered with Z. 
original software needs some index files that I don't
know to generate. 

I seach a mailreader who doesn't need index files (like
mutt) or is able to generate them itself. The mailreader
hast to cope with mail archives with one file is about 8MB
and containing about 5.000 mails. 

thx
Ekkard