Posties on unofficial strike since Monday are due to meet this morning, as a suspended worker is re-instated after a wildcat walkout in Abingdon.
The Oxford Mail reported that millions of items of post will be left undelivered for days as 500 Royal Mail workers in Oxford continue with an unofficial strike.
The employees at the sorting depot in Cowley are involved in a dispute which began on Monday afternoon when post worker and CWU steward Steven Gill was suspended.
Strikers said Mr Gill, who has worked at the depot for 10 years, was suspended without reason.
In a statement, Royal Mail said a second worker had also been suspended.
A meeting on Monday between Communication Workers' Union representative Bob Cullen and Royal Mail management ended in stalemate.
Mr Cullen said: "The action of management is very antagonistic and it was primed to get a reaction. They knew exactly what would happen if they did this.
"They have suspended one, possibly two, people and not even laid a charge against them. If they wanted to stop it, they could stop it in 10 minutes. All we want is the two people reinstated."
Each day a million items of post are sorted at Cowley. Today, managers in shirts and ties were seen driving Royal Mail vans out of the depot.
The Oxford Mail understands managers have been drafted in from other depots across the region to tackle the backload.
Strikers were today told to return to work by a CWU divisional representative because the strike was not official.
An official dispute involves members balloting on action and this being endorsed by the union executive. Employers then require seven days notice of any action.
However, workers decided to continue with their unofficial action.
Royal Mail spokesman Richard Hall said: "Royal Mail is extremely disappointed that despite the CWU renouncing the unofficial action, the union seems to have made little effort to resolve the dispute swiftly, and encourage staff to return to work.
"Royal Mail remain available at any time to discuss the issue at the centre of the dispute, which is being handled in accordance with procedures agreed with the CWU.
"Collections and deliveries have been made today. However disruption to customers is inevitable."
Workers at the Oxford depot will meet at 11am on Thursday to decide the next step.
In a separate dispute at the Abingdon delivery office, in Ock Street, 80 postal workers walked out at 7.30am today after a member of staff was suspended for refusing to take on extra work without pay.
After talks between union officials and managers, the man was reinstated. A Royal Mail spokesman said: "The issue was resolved after 40 minutes. Any staff taking on additional work will receive the appropriate overtime payments."
Update 19 July 2007
Workers voted to continue their strike until at least Monday.