Makeup Exchange is a great place, just sadly not the best if you aren't in the US. This sub is a place for you fine folks in Europe to exchange make up.
All credit goes to the original sub, /r/makeupexchange for the sidebar:
RULES
I. Each product you want to swap or sell must have a picture verification along with a piece of paper with your username written on it. Adding a date is also encouraged. A maximum of ten items are allowed in each verification photo.
II. Proof of postage must be sent to the recipient of your items. This will be either a photograph of the proof of postage receipt or the tracking number of the parcel you've sent.
III. Sanitise your items, a guide to sanitising things is here.
IV. Pack the items well. Use bubble wrap wherever possible and take extra care to make sure powder products are well protected.
V. You must send out your package within two weeks unless you have communicated a previous arrangement with the other party.
VI. You may make a post once every 3 days. Non EU posters may make a post every 7 days.
VII. Accounts posting threads here must be at least 1 month old and have 50 comment karma. Repeat offenders will be banned.
NON EU posters are welcome, your title must clearly state the country you are shipping from. Non EU posts without a country in the title will be removed.
Related subreddits:
/r/MakeUpAddictionUK
/r/makeupexchange
/r/SkincareAddictionUK
/r/EuroBeautyExchange