East Thurrock United defeated Sittingbourne last year in the FA Trophy and this year repeated the feat, this time in the FA Cup.
Sittingbourne were without influential defender James Campbell, missing through a groin strain, Matt Nicholl replacing him.
The game was an even contest until 22 minutes when Mark Cartlidge found himself clear and lobbed Kevin Fewell to put East Thurrock into the lead.
Ten minutes later came a highly controversial incident as Darren Smith lunged at Paul Cobb, he seemed to get the ball cleanly but Referee Mr Biddulph produced a red card.
The sending off gave an edge to the game and the Brickies responded well and apart from an effort from Cobb that went wide they were under little threat for the rest of the half.
Sittingbourne's ten men held East Thurrock at bay in the second half until 57 minutes but then a bullet header from a corner by Kevin Mully increased their lead.
Sittingbourne made all of their three permitted substitutions on 65 minutes but the changes didn't click straight away and after a poor Tom Berry free kick a Thurrock break away ended in Scott Holding blasting the ball wide.
Sittingbourne too were having their moments and a Jon Neal left wing run ended in him crossing to Lee Browning whose shot seemed to be destined for the right hand corner of the goal until Keeper Mark Hardingham tipped the ball round the post.
Sittingbourne pulled a goal back on 72 minutes when Danny Dafter handled the ball in the area. Clint Gooding fired home the penalty at the second attempt after the referee spotted an encroachment in the area and had ordered a retake.
A minute later Gooding went into a challenge with Hardingham and came off second best with an injury to his chest. Although Gooding played on he was effectively a passenger for the rest of the game. This probably put an end to any thought of a comeback and Sittingbourne were then finding it difficult to pose any further threat.
East Thurrock had the best chance of the closing period when right on time substitute Tommy Lee found himself with just Fewell to beat but his hurried shot lurched wide of the goal.
Sittingbourne: Fewell, Coyle, Dowley, Davies, Nicholl (Browning 65 mins), Taylor (C), Berry, Marsh (Gooding 65 mins), Neal, Smith, Spice (Davies 65 mins), sub not used: Beeney