I have been using MCF in the USA for sometime and find it reliable and parcels are fully trackable.
I have recently been trialling using the service in the UK. What a nightmare! They are using a Royal mail service which supplies a tracking number which is not trackable online or recognised by Royal Mail themselves. I have several parcels which have either not had any scanning updates or which show as delivered which the customers have never received and have no proof of delivery. Now CS are refusing to refund these orders even though the required timeframe has passed. This of course leaves me out of pocket for the product, refunds and Amazon MCF fees. Customer Service are being their usual inept selves, the latest case I opened received a point blank this does not qualify for reinbursement, even though it cannot be tracked and has not been received and I supplied copies of comms with with my customer. If it was an order I had sent to an Amazon customer I would have instantly lost an A-Z claim.
I really cannot believe Amazon are continuing to offer this service (or lack of service)