The Irish postal service has issued a warning today advising customers not to send any letters or parcels until further notice.
A strike today will affect An Post’s mail sorting centres across the country, although Post Office retail services will not be affected.
Post will also not be collected from business today.
Staff of IO Systems management, the company responsible for maintaining mail sorting equipment at the sorting centres, are striking today over pay and rostering issues.
A new rostering arrangement could see a pay cut of as much as 22% for some staff, with many placed on non-rotating night shifts for the rest of their time at the company.
The strike is expected to last for two weeks, and for now An Post are warning people not to post anything until advised otherwise.
A statement from the postal service said today: "An Post greatly regrets this inconvenience to our customers and urges the parties involved to resolve their differences through the normal industrial relations procedures."