When you are typing in an email address the website is only checking the format of the email address to see if it is formatted properly. Does it have a @? Does it have a period? Following the period, are there only three characters? Are the three characters after the period COM or ORG or BIZ, etc. I also assume it is looking for only allowbable characters A-Z, 0-9, etc.
There is no master list of email addresses, so the only way to tell if an email address is valid is to send a confirmation email to the email address you entered. If the email does not bounce back then it is assumed to be good. For companies that want to make 100% sure they have a good email address going to the right person they force you to follow a link that 'activates' the email address.
You did not get a Welcome email because the email addresses you entered were bogus and bounced back to the sender. Your actual email address may have had a character in it that Que Pasa didn't like. Maybe a # or $ or something else.
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