Postie plugin – keep in inbox, marked as read, avoid repeat duplicate postings

Present Situation & Problem

At present, the Postie recommends that it be set so that email messages be deleted on the server, after they have been posted.
If there emails are not left on the server, then there is no record/backup of the email.

If the setting is changed so that email is left on the server, then Postie continues to download the emails and post them repeatedly, making duplicates at what ever the checking interval time is.
This is because Postie has no setting to restrict them emails that it converts to posts, by only checking the “unread” or “as yet un-downloaded” emails.

Suggestion
It would be handy to have capability & settings in Postie to;

a) only download the unread emails (to avoid duplicates, while leaving copies on the server). This setting could alternatively be called “leave originals on server”.

b) re-download all emails and convert to postings
This allows the use of the emails as a backup, if ever the website gets a major revamp and the postings are damaged, or the whole blogging section has been deleted.

c) the content for the website can be created even well before the website is designed, and when the website is designed, then Postie will automatically add in all the content. No nonsense for the copy writers or the usual staff.

Additional Feature might be to allow control of message flushing from the email account, after a predetermined time delay.