Outside of Dublin and Northern Ireland, postal codes aren't used; what's more important here is the county, so be sure to include it when addressing an envelope.
Letters by standard post take a week to 10 days to reach the United States and Canada, 3 to 5 days to reach the United Kingdom.
Airmail rates to the United States and Canada from the Irish Republic are €1 for letters and postcards. Rates are €1 for letters and postcards to Europe. Mail to overseas can be sent economy or airmail. Letters and postcards within the island of Ireland cost €0.68.
Rates from Northern Ireland are 97p for letters and postcards (not over 10 grams) to continental Europe, the United States, Canada, Australia, and New Zealand. To the rest of the United Kingdom and the Irish Republic, rates are 62p for first-class letters and 53p for second-class.
Mail can be held for collection at any post office for free for up to three months. It should be addressed to the recipient "c/o Poste Restante." In Dublin, use the General Post Office. The postal service in the Republic of Ireland, known as An Post, has a website with a branch locator and lots of other postal information. In Northern Ireland mail service is run by the Royal Mail.
An Post. 01/705–7600; www.anpost.ie.
General Post Office. O'Connell St., Dublin, Co. Dublin, 1. 01/705–8833.