This is all true, but suspect that the issue is mostly self-correcting since anything other than an extremely vanilla email address is likely to run into an infuriatingly high number of rejections precisely because the software at the other end has taken an overly simplistic view of what is allowed, forcing the owner to change it out of sheer frustration.
Prompt: "URL regex"
Prompt: "Email regex" This one's weirdly sophisticated for some reason.Prompt: "An HTML tag with a close tag and attributes"