It’s pretty simple really.
No mail carrier charges VAT on their postage service.
Couriers all charge VAT on their postage service.
If you buy into the EU from outside you pay no VAT or Sales Tax and you pay postage where applicable. When that parcel lands in, say Ireland, the ‘total’ value of that parcel on your invoice including all postage and packing and other fees is the amount An Post will charge VAT on.
Buy £100 of models from the UK and pay £10 postage then An Post see a £110 parcel and will apply 23% VAT on £110 / €130 or so. You will therefore pay €159.90 in this example plus the An Post fee for handling the import VAT for you, which seems to be a range between €3.50 and €6.50 presumably based on value