I have pasted below the guidelines from the FKT website.
So a question came up in conversation with some hiking friends - would mail drops be considered supported or self-supported? Would it make a difference if you mailed all your own mail drops ahead of time or had someone send them?
Here's a few points that were made:
if you mail all your mail drops ahead of time, this would/should be considered self-supported as that option is "equally available to anyone else."
if you have someone mail them, would that be considered an option that is NOT "equally available to anyone else?" ie - no one willing to do it and this considered SUPPORTED?
Does ordering anything from Amazon or a vendor change your trek from self supported to supported? This option IS available to anyone else who can afford it. Wouldn't this be the same as "buying supplies along the way" which is part of being "self-supported?"
Self-Supported
Self-Supported means you may have as much support as you can manage or find along the way, but not from any thing or person just for you; any support you employ must be equally available to anyone else. This can range from caching supplies in advance, purchasing supplies along the way, staying at motels, to finding or begging for food or water; camping in a friends yard would be Supported, because that is not available to the public. Most long thru-hiking routes are done Self-Supported. To get a Self-Supported FKT you also have to beat the fastest Unsupported time. Spectating will be considered as Support starting February 4, 2021 (no previous FKT classifications will be changed).
Supported
Supported trips can have as much support means you can enlist, as long as you are entirely self-powered. This can range from one person handing you water once, to an entire team that accompanies you the whole distance giving you everything (except physical assistance). Whether it’s just once or continuously, any support at all means it’s a Supported trip. On longer routes, Supported can enable the fastest trips due to the ability to carry less weight. To get a Supported FKT you also have to beat the fastest Self-Supported and Unsupported times.