I accidentally hit reply-all on an email and sent an email to company that sends me emails, but I shouldn’t to reply directly.

Gmail doesn’t have an option to warn you for emailing certain people or domains, so I wrote a Tampermonkey script to stop this.  To use, install Tampermonkey, then when you’re on gmail.com click the Tampermonkey icon, create script, then paste in this script, changing the domain to whatever domain you don’t want to email.

Here’s the script: https://pastebin.com/1zDaWGDU