After a goalless first half, Richards’ excellent volley on 51 minutes gave the Hornets the lead.
Malins’ fine header secured Horsham’s first victory of pre-season with a minute of normal time remaining.
The Hornets continue their pre-season programme with a trip to old friends Dorking Wanderers this Tuesday (7.45pm).
See some pictures by the club's photographer John Lines on this page and the ones linked.
Get the latest from the Camping World Community Stadium in the West Sussex County Times - out every Thursday.
1. Horsham 2, Maidstone United 0 - the match in pictures
Action from Horsham's pre-season victory over National League South outfit Maidstone United Photo: John Lines
2. Horsham 2, Maidstone United 0 - the match in pictures
Action from Horsham's pre-season victory over National League South outfit Maidstone United Photo: John Lines
3. Horsham 2, Maidstone United 0 - the match in pictures
Action from Horsham's pre-season victory over National League South outfit Maidstone United Photo: John Lines
4. Horsham 2, Maidstone United 0 - the match in pictures
Action from Horsham's pre-season victory over National League South outfit Maidstone United Photo: John Lines