This article is from the alt-sources-mac FAQ, by Mark Pilgrim (firstname.lastname@example.org) with numerous contributions by others.
Large source archives (for instance, code and resources for an entire
program) are problematic, because some users must download an entire news
article to read it. Also, some newsreaders will cut off very large posts
(over 1000 lines). Therefore, put all relevant information about the
source code in the first post, labeled "part 0 of n", where n is the number
of posts the source code is split into.
After the informational post, the source code itself should be compressed
and BinHexed. (Compact Pro and Stuffit Lite are the favored compression
programs, and the compressed archive should then be converted to BinHex 4.0
format with any program that does that sort of thing. Compact Pro and
BinHex both do this quite well.)
The BinHex file should be split into sections of no more than 800 lines each.
In unix, this can be accomplished with the command
split -800 filename
Each post should have a subject line that contains the part number ("part 0
of n" for the informational post, "part 1 of n" for the first 800 lines of
BinHexed source code, "part 2 of n", etc.). Remember, these subject lines
are used as indices when your source code gets archived on ftp sites (see