QB Desktop flagging email addresses as invalid

Thank you for your response Kristine. However, I don't see how that can be true for multiple reasons:

• ISPs are not the same as webmail providers (Gmail, Yahoo, Hotmail, etc). Regardless, to the best of my knowledge there is nothing that a software provider like Quickbooks (or the IRS) would need to "support" when it comes to Email. Email is an address, and directing mail to that address doesn't require any support, integration, or other setup with the email hosting provider.
  • It's like snail mail in a way. Your shipping department doesn't need to "support" commercial building addresses. You just put the address on the letter and the delivery agent (USPS, Fedex, etc) handles getting it to the right place.
• Thousands (millions?) of businesses use Quickbooks. If what you said is true, that would mean not only can none of them use their own business email addresses to E-file, but they would be forced to use an unsecure, non-corporate, webmail address to handle their sensitive E-file and tax information. There's no way that would be acceptable to thousands of your customers.
• I do not see anything in the articles you linked stating the email address has to be from a webmail provider. However in the 2nd article, I do see a couple images that specifically show the example email address as <[email address removed]> which directly implies the address is a company-specific domain, *not* forced to be a webmail provider. (See attached image.)

My best guess is Quickbooks (like many other companies) has some email fields in their software where they haven't updated the error validation code on the back-end to account for the fact that there are now many, many valid top-level domains besides just .com, .net, and .org. This was mostly 2012-2015 though, so not exactly a recent development.