Crawley Town fought back from 2-0 down at half-time to take this FA Cup first round replay to extra-time - but four Southend goals in the extra 30 minutes saw the Essex side through.
The Reds were inspired by a brilliant double from top scorer Ollie Palmer. But the comeback would not have been possible if it was not for another brilliant display by keeper Glenn Morris, who made a string of good saves.
But the extra time proved too much for the Reds as Southend were clinical to add four more goals. They will now face Barnsley in the second round on December 1.
Gabriele Cioffi has made four changes to the side who lost to Grimsby Town at the weekend. Felipe Morais, Luke Gambin, Josh Doherty and Bondz N'Gala come in for Dannie Bulman, Joe McNerney, Joe Maguire and Ashley Nathaniel-George.
Great work from Ollie Palmer forced an early corner for the Reds but Mark Connolly headed wide from Doherty's corner. Palmer was looking dangerous up front and on 11 minutes he forced an outstanding save from Mark Oxley - but it would not have counted as referee Charles Breakspear gave handball against the striker.
It was from the visitors' first real attack on 17 minutes that they took the lead - and there was some confusion about the goal. Harry Bunn made a run down the left and his cross seemed to be turned in by Simon Cox. But the goal was awarded as an own goal by Josh Doherty.
Josh Payne was then booked for a foul. Crawley were still playing some nice football and on 29 minutes looked like they had a clear chance to equalise when the ball fell nicely to Camara 12 yards out by Gambin appeared to get in his way just as he was about the strike the ball.
But on 31 minutes, Reds were two down. Stephen McLaughlin broke down the right and crossed in. Cox's header was brilliantly saved by Morris but Bunn was quickest to react and fired home from two yards out.
It could have been 3-0 on 40 minutes when McLaughlin broke and laid off to Cox, but the striker fired into the side-netting.
Crawley needed something in the second half if they were going to get anything from this game Cioffi made an immediate change at half-time, bringing on Nathaniel-George to replace the ineffective Francomb.
But it was Southend who were still on top and should have gone 3-0 up when Cox found him himself in front of goal but Morris saved at his feet, before the stopper saved again, this time from Theo Robinson. And those saves looked like they could be vital when on 55 minutes the Reds were back in it.
Young found Morais and his cross found Palmer in the box who calmly took a touch then fired home past Oxley. And that goal certainly got the crowd going.
Southend were still very dangerous on the attack and on 65 minutes had a chance to get a pivotal third goal, but Robinson fluffed his shot after a lovely lay-off from Timothee Dieng.
The next goal would be vital and it proved so when Palmer got his second of the game. He got the ball with his back to goal on the edge of the area, turned and powered past two defenders before coolly slotting home.
And the striker had a chanace for a hat-trick when he sensationally controlled a long ball - but his shot was deflected wide.
The Broadfield Stadium had a real cup atmosphere and the fans replicated what they did at Roots Hall.
But the wind was knocked out of Crawley's sails two minutes into extra time. Crawley faied to clear a McLaughlin cross and the dangerous Cox's shot took a deflection and Morris couldn't save it. It was a disappointingly soft goal to concede.
And just five minutes later it was 4-2 when John White volleyed home from a Mantom free-kick. It was a tall order for the Reds to produce a similar fightback from here and unfortunately i was not to be. Within a minute of the second period kicking off, Mantom scored to make it 5-2.
McLaughlin then made it 6-2. Crawley did not deserve to be beaten by four clear goals but in the end the extra-time was a step to far. And it could have been seven if it wasn't for a stunning goalline clearamnce by Connolly at the end.
CRAWLEY TOWN: Morris, Young, Doherty, Payne (Poleon), Connolly, Palmer, Gambin (Grego-Cox), Francomb (Nathaniel-George 45), Morais, Camara, N'Gala. Subs: Mersin, McNerney, Grego-Cox, Poleon, Nathaniel-George, Maguire, Bulman.
SOUTHEND UNITED: Oxley, Demetriou, Moore, White, Kyprianou, McLoughlin, Dieng, Hyam (Mantom), Bunn, Cox (Hendrie), Robinson (McCoulsky). Subs: Bishop, Bwomono, Hnedrie, Knightly, Mantom, Klass, McCoulsky.
SEE ALSO FA Cup: Crawley Town v Southend United - the line-ups | Crawley Town verdict: Last week was good, hopefully the week ahead is one of excitement and hope rather than one of fighting and fear | Crawley Town fan's view: Season is delicately balanced on a tightrope | Ex-Leeds United and Barnsley manager Paul Heckingbottom wanted by Notts County - League 2 Live Blog