Following in from
https://www.theanswerbank.co.uk/Technology/Computers/Question1613244.html
To be honest as I read through what I put last time it is the same issue, but she is now asking about e-mail clients she can buy, and I figure if Thunderbird isn't working why should a paid for client ?
A couple of examples, a few days ago she replied to a received e-mail, on sending it came up with some error message that it couldn't put it into the SEND box/folder. We've come across this before, and it means it isn't to be found on her PC client, nor on the website account, nor on the mobile. It may have been sent, it may not have; no way of telling. But for sure the e-mail is now nowhere to be found and has no evidence of being written any longer, until someone responds, if they do.
She got confirmation from the person sent to that it wasn't received so send the same info again just now, from my modem/router, using her mobile phone. No message came up about there being problems putting it in the send box, and it went into the send box on the mobile client just fine, but checking her PC and the service provider's webpage for her e-mail account, nothing is seen.
Any thoughts what the issue could be and how to fix it ? I feel IMAP must be part of the problem, the the strange combination of what works when, and what doesn't, is puzzling.
TIA