An Post has reduced the weight of post and parcels it will send to Ukraine for free.
The postal service says this is due to how busy its services are in the run up to the Christmas period.
Under the new rules, which came into effect yesterday, all items over 2kg will incur normal postal charges.
Any items under 2kg will be free until at least January of next year, but limited to one item per transaction.
In a statement An Post said it is committed to providing free postage to Ukraine.
But it said the introduction of charges for heavier items is necessary "due to peak seasonal volumes and to preserve the service quality, to ensure delivery of items to Ukraine".
An Post says that it has handled more than 43,000 mail items since the start of the free postage offer to Ukraine. The company says that that figure will exceed 50,000 in the coming weeks.
The post is shipped through Air Business, An Post's logistics and distribution firm in north-west London, to Poland’s Poczta Post then on to Ukrposhta, the Ukraine postal service.
Among the items sent in care packages since then have been clothes, baby food, pet food, shoes, medical supplies, bed linen, and educational toys.
An Post says mail to Ukraine has been taking up to six weeks given the complexity of delivering mail to the war-torn country.
It has adjusted its regular Christmas posting time to give Ukraine mailers the best possible chance of getting letters and parcels through in good time, and it says the recommended last date of posting to Ukraine before Christmas is 9 December.