Postal services in Dublin and in counties Wicklow, Louth, Monaghan, Meath and Galway are paralysed after An Post yesterday suspended 192 staff in Dublin's primary mail sorting centre.
The staff had refused to carry out certain work practices.
The Communications Workers Union and An Post are engaged in a dispute over pay and employee share options.
The CWU apparently told its members in Dublin's main mail centre not to carry out certain duties which, it claims, are new work practices, but An Post says have been in place for the last year.
64 were initially suspended, with the figures rising as the dispute continued.
Until further notice, customers are being told not to post mail to or from Dublin, Bray, Greystones, Wicklow town, Carrickmacross, Castleblaney, Drogheda, Dundalk, Kells, Navan or Tuam.