It is too early to say the solutions recommended don't work. You have apparently misconstrued the issue about the e-mail address. Of course the e-mail address is written out in full when you send an e-mail. But you need to check that in the app e-mail settings the entry for the username uses the e-mail address in full. Once you have confirmed this one way or the other we can advise further.
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Also just done another experiment. It will send from a different wifi network - in this case The Cloud in local Wetherspoon, so what was said about VM security concerns does not really ring true. Surely 4g is more secure than a public wifi?