re :''purpose for a @thunderbird.com email account is only to be used as a recovery email account for my protonmail email accounts. '' Creating a non existant account is futile. What you do not say is where the emails in your protonmail account currently reside. Are they only on the server and you currently access this via a browser, but you are looking for a means of backing them up? Do you already have existing mail accounts in Thunderbird because it sounds as if you do not ? If no: Just set up mail accounts to use your current valid existing email addresses and download the emails. Menu icon > New Message > Existing mail account Pop mail accounts only download from server Inbox, but auto save emails in Thunderbird Profile. Make sure you select to 'Leave messages on server' if you want to keep copies of them on server. Imap accounts see a remote view of subscribed folders on the server. Make sure you synchronise and download for offline use to get copies into Thunderbird, otherwise you may only store headers. Thunderbird already has a default mail account called 'Local Folders'. You could use 'Local Folders' mail account to store emails, you would manually move/copy or use a Message Filter to move them into 'Local Folders' mail account. It does not connect to any server. https://support.mozilla.org/en-US/kb/automatic-account-configuration https://support.mozilla.org/en-US/kb/imap-synchronization