Why are 'spam and search' difficult-to-impossible in a native app?
For that matter, why are you equating 'the web' and 'server-side'? The standads IMAP protocol stores messages server-side while also enabling effecient server-side search. The standard managesieve protocol implements support for managing server-side filters from remote clients. Tools such as SpamAssassin perform intelligent per-user filtering server-side.
At that point, the only real differences between webmail and native clients are:
- UX
- Native clients use standardized protocols by default.
For one thing Spamassassin is quite hopeless compared to Gmail's filter (and yes I have compared). But more to the point I would absolutely equate web with server-side hosted app. For example, if you want to implement decent search it's probably going to be Lucene-based. So if you are just talking thin-client presentation layer, the app isn't really native in any case - the acid test for a non-web app is whether it works without an internet connection. (Other major differences would be ubiquity and maintenance.)
For that matter, why are you equating 'the web' and 'server-side'? The standads IMAP protocol stores messages server-side while also enabling effecient server-side search. The standard managesieve protocol implements support for managing server-side filters from remote clients. Tools such as SpamAssassin perform intelligent per-user filtering server-side.
At that point, the only real differences between webmail and native clients are:
- UX
- Native clients use standardized protocols by default.