None i have tried during the purchase process get a green light under the email, some are red some are black some are green and red, but non all green.
RedFox has (currently) 4 mail servers, 3 of them are "bundled" to one mail system for all RedFox mails. The other mail server is dedicated to forum emails only.
When you try to order, our server is doing two checks with the email address entered, just to make sure it is valid:
1) syntax check for
name@domain.tld
2) Each of our 3 servers tries to connect your mail server and ask friendly if we are allowed to send the email to
name@domain.tld and if the user and domain exists.
You might already guess it: the 3 lights are representing our 3 mail servers. Green is OK, red: your mail server does not accept email at all from this redfox server, blue: your mail server replies "I accept emails, but don't tell you if user exists (e.g. yahoo does this), black: user unknown at recipients mail server.
Although we do these checks, a lot of people are having typos in their email address. If an email (from support, order, forum etc) to a customer bounces, I'll check them manually and try to find out what's wrong. E.g. if customers mail server denies mails from server A, I route mails to customers mail domain through server B or server C and re-sent the email.
So if you at least ONE green light, you are safe.
Even if everything is black, you'll get emails from RedFox, but maybe with a delay of ~1 day.
Good free mail services are gmail.com, protonmail.com...