I have two email accounts one a lineone account and one a tiscali account. When I try to add the lineone account to my email list I get the message that the account does not exist - as I have had this account for many years I know that it does exist and I can access it through webmail or Thunderbird. When I try to add the tiscali account to my email list I get the message that this address is linked to another account - I do not know which other account as this is most definitely my email account and has been for many years.
On a separate subject, the lineone account appears to have been emptied overnight as there was nothing in either the inbox or deleted mails this morning.