I would like to ask you what is the best practice to use Webtop 5 on a Smartphone?
I’d say ActiveSync…
You can use eg. IMAP, but you’ld be missing out on a lot of features.
My 2 cents
And there is no special Webtop 5 mobile App?
IMAP for mail
ActiveSync or DAV for calendars and contacts
DAV (CalDAV and CardDAV) are already present in iOS. For android it suggests to use DavX5