An Post has advised customers not to post any letters or parcels until further notice.
The company has blamed industrial action by members of the Communications Workers’ Union (CWU) in mails processing centres of supplier company IO Systems for the announcement.
Post Office retail services are not affected.
According to the union, the CWU National Executive unanimously backed and endorsed the strike action at an emergency meeting this morning “to defend the rights of IO Systems workers”.
An Post have released a statement.
"An Post greatly regrets to advise customers not to post any mail items, with immediate effect," the statement read.
"Also, as a result of this industrial action, there will be no mail collections from businesses today, Friday.
"Due to the withdrawal of labour by staff of IO Systems, we are unable to process mail for delivery to customers.
"Mail deliveries are operating as normal today. A small number of letters were not processed last night due to the industrial action between IO Systems and the CWU.
"An Post greatly regrets this inconvenience to our customers and urges the parties involved to resolve their differences through the normal industrial relations procedures."
The union has accused An Post of “blackmailing” postal workers, describing the company’s decision to suspend postal services as “bizarre”.
The union says the strike has “total solidarity and support from postal workers at An Post”.
Commenting, CWU General Secretary Steve Fitzpatrick said: “The decision of the company to close mail services is bizarre and reckless and will have long term damaging consequences for postal services in Ireland and industrial relations at the company.
“We have had our suspicions up to now and these have been confirmed by the irrational action of the Company to escalate this dispute threatening a €850m business to save €100,000 in wages to less than 30 workers at IO Systems.
“We are calling today for the appointment of a Special Investigator from the C&AG’s office to examine the background and process for the awarding of the IO Systems contract by An Post.
“We are appalled that well paid An Post executives are supporting IO Systems management in seeking to cut wages and consign IO Systems workers to permanent night work without proper recognition in their pay and conditions.
“Severe amnesia has clearly set in among management at the company who have quickly forgotten the sacrifice in time, money and working conditions that postal workers have made to keep the company afloat during the technology revolution and the traumatic and devastating economic depression.
“This sacrifice clearly counts for nothing to the company that has abandoned all semblance of a positive industrial relations environment to defend the dubious contract it has entered with IO Systems.
“We will not back down in the face of this provocation and threats from the company.”
Fianna Fáil Councillor Cormac Devlin raised concerns that the industrial action at An Post will hit up to 82,000 social welfare recipients who receive their payments by post.
Councillor Devlin said: “This industrial action will affect up to 82,000 individuals in receipt of cheque payments from the Department of Social Protection.
"Around 68,000 of these who receive their Jobseekers’ payments by cheque may be affected.
"Almost 9,300 customers who receive illness, disability and caring benefits may also be affected.
“This issue is causing significant distress to people in receipt of these weekly payments. Any delay has the potential to cause considerable hardship for some.
"I am calling on Minister Joan Burton to immediately confirm what contingencies her department has in place to deal with this issue.”