No worries. It's still a nice way of understanding it.
Googled it and found that "pepo" means both the plural of wind and also demon or spirit. Spirit mail? :P
I have learned this/seen it in Swahili books before, but I've never actually heard it used, and I tried it one time and got a funny look. Maybe I'm in an area with too much influence, but people here just say "e-mail."