Royal Mail and the Communication Workers Union have made "significant progress" in avoiding stike action at the recently privatised business.
In a joint statement, both parties said progress had been made in talks over legal protections, pay and industrial stability for workers.
To allow discussions to continue, the legal validity of the ballot for industrial action has been extended by another seven days until 27 November.
The union had previously allowed until today (13 November) for an agreement to be reached after it called off a 24-hour strike at Royal Mail and Parcelforce, which has been planned for the 4 November.
If a strike is to go ahead, it will affect all non-managerial positions at the two operations.
Yesterday, Unite union members at rival carrier UPS’s Camden depot voted to strike over being forced to handle “unreasonable” workloads, a claim UPS has refuted.