Our handling charges, and your mail forwarding options, are based upon a set of very precise size and weight limits, defined by the Royal Mail and described in more detail below.
Something to consider: Although classed as a 'Letter' for the purpose of calculating our handling charge on delivery, this same letter may incur 'Large Letter' Royal Mail postage when forwarded as a single item, simply because the tamper-proof postal bag in which it is enclosed adds to the overall dimensions. This is rarely important, however, because we are almost always forwarding several letters in the same bag!
a letter is, just a letter!
To be classed as a Letter, an item must be under 100gm in weight, no larger than 24cm x 16.5cm, and less than 5mm in thickness.
when is it a large letter?
The next step up, with a maximum size of 35.3cm x 25cm and up to 2.5cm, (1 inch) thick is the Large Letter format.
A Large Letter can weigh as much as 750gm and might contain things like A4 documents, cased DVDs or magazines.
...or a parcel?
The Small Parcel format, weighing up to 2Kg and with a maximum size of 45cm x 35cm x 16cm, can be carried by Royal Mail 1st Class post to addresses within the UK and abroad, just like the two letter formats.
You can, however, use your mailbox for items up to 20Kg in weight and as large as 61cm x 46cm x 46cm ( the Royal Mail's Medium Parcel limits ) at no extra charge, but they must be forwarded by Courier.