@engineer,
From 1 October 2015 onwards, all short-stay visa applicants have to appear in person when lodging the application, in order to provide their fingerprints.
Reason: as from 1 October 2015, the Spanish Embassy is using the Visa Information System (VIS), a central database for the exchange of data on short-stay visas (for stays up to 90 days in any 180-day period) between Schengen States.