Newport closed their ticket office ahead of the FA Cup fourth-round tie against Manchester United after staff suffered “appalling abuse and threatening behaviour”.
The Welsh minnows host the Premier League giants at a sold out Rodney Parade on Sunday – the first-ever meeting between the two clubs.
Remaining tickets on Monday were only made available for purchase online after the Sky Bet League Two club closed its ticket office.
“Unfortunately, this decision has been made after the appalling abuse and threatening behaviour the ticket office and support staff received during the priority purchase period on Thursday,” Newport said in a club statement.
“The club will not condone this behaviour towards any member of its staff and will employ a zero-tolerance policy going forward which may result in stadium bans or legal action.
“The club’s small pool of staff has worked extremely hard across long hours in recent weeks to organise the two sell-out games against Wrexham and Manchester United.
“The club would like to thank them for their dedication and commitment.”
A crowd of around 10,000 is expected after Newport increased capacity by erecting a temporary stand behind one of the goals at Rodney Parade.
Providing an update on Monday, Newport said on X, formerly Twitter: “We can confirm that all tickets for our #EmiratesFACup clash with Manchester United have now sold out. Thank you for your fantastic support.”
Newport manager Graham Coughlan has called the visit of 12-time cup winners United as the “biggest game” in the club’s history.
The in-form Exiles, who stand to make £400,000 from the televised tie, extended their unbeaten run to seven games on Saturday by beating Welsh rivals Wrexham 1-0 at home.