Maybe they use something like https://getemails.com/ ? It works only for emails but basically the same scenario. Source: about 2 years ago

I haven't had exposure to this space since the GDPR went into effect, but it used to be trivially easy to do this. A quick Googling shows there are still providers of this sort of service, such as GetEmails[1] which bills itself as '100% compliant in the US'. [1] https://getemails.com/. - Source: Hacker News / about 3 years ago

Caucasian person wearing pink t-shirt with an illustration from Nathan Pyle's Strange Planet called "Creature Restoration Specialist" from threadless.com, and Walmart brand pull on black and white pinstriped cuffed shorts, and a pastel blue Castro hat. Long brown hair and glasses on person. Standing in front of a mirror with camera phone and other hand in belt loop. Source: 11 months ago

Hello, checkout my store :) I just opened a shop on threadless.com I sell everything ranging from jigsaw puzzles, coffee mugs, art (framed or unframed), to buttons :). Source: about 1 year ago

Might want to check the requirements at a website like threadless that produces products based on designs. Either way keep creating:3. Source: over 1 year ago

Threadless.com: For artist lovers out there who want cool art on cool gear. They have frequent sales going on, especially around the holidays. (My favorite artists on this site are nathanwpyles, wicdiv, and ohlookitsdae.). Source: over 1 year ago

I own this as a tshirt. I found it on threadless.com, not sure if it's still there. Source: about 2 years ago