Talks are ongoing between An Post and the Irish Postmasters' Union (IPU) in Malahide, Co Dublin, to try and avert a postal strike next week.
Both sides are discussing a threat to disrupt the sorting of mail from Monday next. Any industrial action could delay delivery of CAO offers to school-leavers.
The IPU claims allowances for early morning work are insufficient and that staff are not paid at all for some other duties.
An Post runs 100 of the country's 1,800 post offices, with the rest managed by members of the IPU as sub-contractors.