I am searching items with AdvancedSearch method.
Where I can get detailed information about search filter format?
All these "urn:schemas:mailheader:subject like 'test'"
I found some about urn:schemas:mailheader: namespace
http://msdn.microsoft.com/library/de...ff45ca0b60.asp
But still cant find anything about filter itself.

From the reference:
Performs a search based on a specified Microsoft SQL Server search
string and returns a Search object
Filter Optional Variant. The DASL search filter that defines the
parameters of the search

What is "Microsoft SQL Server search string"? What is "DASL search filter"?