Mailing perfume domestically.

I'm international and I've done a fair amount of BPAL swapping myself, obviously most internationally and about half with US residents. To echo the earlier comment, perfume oils are fine, but from American friends' accounts, it can also vary depending on which postal worker you get, your specific postal office, etc. since some of them won't know enough--i.e. there are perfume without alcohol! Etc. So it can be important to make sure you get a postal worker that you can talk to and is reasonable. I've had a postal worker personally (here in Singapore) whose only concern was that if the item will break and spill, so that could be an additional thing--make sure they know you have the precious wrapped snugly and everything. For me it's usually some form of non sticky tape on the lids, And then a small ziploc baggie per bottle, and then bubble wrapped individually, inside a bubble envelope. For imps or decants, plumber's tape, a bunch of imps per ziploc, then bubble wrap. The stuff I've received from the US are also packaged like this. Also usually labeled something innocuous like 'bath items'.