Is there a webmail client or iOS mail app that can reliable search *all* mail?

[murgero]

@robi Edison is a pretty slick client, and would probably do what OP is looking for, but it keeps a copy of your email and just in general has a scummy privacy policy.

[necrevistonnezr]

@murgero As i said, Preside does all what I need and handles all data (including a full-text search index) on device, only.