Mailsort was not widely known to the British public and the code was not written as part of the address; rather it appears elsewhere on the envelope or label.
Unlike posting by ordinary mail it was possible to specify service levels other than 1st or 2nd class with longer delivery times offered.
Four Mailsort products were available – known as 70, 120, 700 and 1400 – each based on the customer's ability to sort into increasingly smaller geographical areas.
A further Walksort product was available to those who wished to post to many of the addresses in an area[2] and who could present mail sorted first by mailsort code and then by walk number (the second half of the postcode).
These services were similar to Mailsort 1400 but offered a greater discount for publications that met certain criteria and had been successfully registered with Royal Mail.