I rarely see a big textbox on the top of the main page of any mailing list archive that says "Fulltext search" (and isn't totally crap). "NNTP Gateway" doesn't sound encouraging in that it is explained and available for the layperson to easily employ as search tool.
I'm actually of the opinion that it would have been better to have a NNTP server to host various newsgroups instead of having various mailing lists. This would have made it much easier to view previous messages posted to the group and would have made it much easier to browse by those who don't participate.
The disadvantage is that it would require one to create an account on another server instead of just using one's existing email account for communication.
As for explaining and availability, I believe the vast majority of people would use search engine to figure out what steps are involved once something like that is mentioned.
