The app description mentions "reMail needs less space than you think: 100,000 emails take 500 MB on your phone - 6% of the capacity of an 8 GB iPhone, the smallest iPhone available"
What does that mean? If I have 1GB size 100,000 emails will that take 500MB of space on my phone?
My 45,000+ messages take 170mb. I've been using Remail for a few months now and find it indispensable. For an idea of how useful it is to me, I sort my apps by frequency of use and reMail is on page 2 of 6, after OmniFocus but before Mint.com.
It's one of those apps I didn't know I needed but use all the time now that I've got it.
It's not a mail app, it's a search index. Like X1 Search (Windows desktop search application) except on the iPhone and indexing Gmail/IMAP accounts. Its settings are separate from the iPhone's Mail app.