Alice tells me that they get quite a bit of philatelic mail for postmarking. So this is all done here in real time in the Post office.
I brought Aitutaki stamps with my that I purchased from the Agent in the USA. Needless to say the stamps had not been put on sale here . There is no First Day Cover service here or in the Cook Islands. Those covers are all postmarked in the USA by the Agent.
Just like the rest of the Cook Islands the Post office is now Blue Sky.