Mail is treated as freight (and thus goods) for the purposes of the place of supply of services rules and the zero- rating for international freight transport.
Supplies to business customers belonging outside the UK are outside the scope of UK VAT.
Supplies to business customers belonging in the UK are zero-rated in respect of mail being delivered to or from a place outside the EU.
Supplies to non-business customers in the case of:
- mail going to or from the UK to a place outside the EU is zero-rated/outside the scope of UK VAT;
- mail going from the UK to an address within the EU is exempt or standard-rated, depending on the service involved.
There is more about this in VAT Notice 744B: Freight transport and associated services.