An Post will no longer deliver wrongly addressed mail free of charge. It said it is no longer possible to simply write a new address on a letter and repost it -- a new stamp must be bought.
An Post's worsening financial situation has forced it to clamp down on the manual redirection of letters, which was never formally allowed by the company.
A spokesperson said there was a range of redirection services introduced by the company in recent years and that it was not feasible to rely on tenants to forward post.
An Post says people moving house or business address should use its redirection service, costing up to €150 a year.
She said the move was justified as the handling cost to An Post for redirected mail was the same as or even more than when it was first posted.
The group reported an operating profit of €5.7m for 2009 mainly due to a 10pc fall in traditional mail volumes. Turnover was listed at €804.2m, down 5.4pc from €850m in 2008.