Reckon One (wrongly) rejects as invalid any email address that has a period in the username portion of the email address, i.e. the character string to the left of the "@". For example ...
michael.done@mydomain.com ... is rejected because of the period between my first name and my surname. But this is a perfectly valid email structure. In fact, many of my client organisations (universities) use the "<firstname>.<surname>" structure as their organisational standard. This means I'm unable to store emails for any of my student customers in those universities, and I can't email invoices to any of them either.
Instead I have to do a Print Invoice to display it in my browser, then save the displayed invoice using Save Page As (PDF), then create an email to my client in Outlook and attach the exported invoice to it. Apart from needlessly consuming my time, this process means Reckon One shows no history of my having emailed the invoice.
Unless I'm missing something really obvious, this is a pretty fundamental flaw and I'd be very grateful if someone from Reckon could either set me straight on what I'm doing wrong, or put this forward to their programming team as a significant bug.