Hope this is the right place to post! 

I would like to mail cookies to a friend in England. From past experiences, it only takes 4 days to get packages between our locations.  From my understanding you are not supposed to mail "homemade" food or things that are perishable.  Cookies do not have to be refrigerated and my business is in my home so I'm sort of confused.  I have read the rules on the post office site, but I feel there is a lot of gray area!

Has anyone mailed something they made to the UK with success? 

me, if you're not supposed to per the usps i would not do it -- or go to the post office and talk to the inspecter there, the head person i can't remember the right title but someone high up the chain of command 

and you're right it depends on the size/level of business you maintain so for a broad example -- swiss colony maybe can ship internationally but i don't think home based businesses under cottage rules would be in that category --

here's an example of international shipping being allowed: collins street bakery

https://www.collinstreet.com/51FPB5_final.pdf

then wolferman's only goes to canada with some items nothing outside of that that i can see

https://www.wolfermans.com/w/view/custserv-handling

it's a very big deal to ship anything so i'd stay firmly within the rules myself -- there's tons of hoops to jump through to do it successfully and legally so those are my thoughts on the subject

*me, if you're not supposed to ship per the usps...

in fact, here's swiss colony's thing about shipping outside the u.s.

Rules for businesses are often different than for personal use. If you want to mail a food package to family or friends, check with the post office.

However, in regards to home processor rules, mailing baked goods across state lines is most likely not allowed under any state's cottage food law.