No maps and nothing on their services page. Though apparently you can attend mass and then confess before flying away. (I can’t imagine what they’ve heard….)
Robert found a An Post drop box:
When exiting customs in terminal 2 – Look to the right in front of bank of Ireland. Green mailbox. Pick up is at 530pm.
Note that An Post boxes are green.
It appears that Google Images search has identified several boxes in Terminal 2 – visit this link for what they can look like.
Last updated 18 August 2018.