Hello, Thank you again. Logged in via basic mail ok but could not send: Requested action not taken: mailbox unavailable 550 <{mailbox}@{username}.plus.com> invalid address '{mailbox}@{username}.plus.com So: - yes to q1 - not sure what 'secondary' means, it is one of several in addition to default mailbox (which is used only for plusnet account communications). It's a few years since I added a mailbox (also deleted one or two); up to now no issues. - I was only aware of username+mailbox format, tried email address also, got same 'login failed' response. I routinely use pop3, would need a substantial change of MO to switch to IMAP. Regards
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