restore.md in imap-backup-4.0.1

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 # FAQ
 
 # How does restore work?
 
+Backed-up emails are pushed to the IMAP server.
+If there are clashes, folders are renamed.
+
 # What are all these 'INBOX.12345' files?
 
+If, when the backup is launched, the IMAP server contains a folder with
+the same name, but different history to the local backup, the local
+emails cannot simply be added to the existing folder.
+
+In this case, a numeric suffix is added to the **local** folder,
+before it is restored.
+
+In this way, old and new emails are kept separate.
+
 # Will my email get overwritten?
+
+No.
+
+Emails are identified by folder and a specific email id. Any email that
+is already on the server is skipped.
 
 ## How do I restore to a different service?
 
 1. Run setup and add the new server, (but don't run any backups),
 2. Rename of the existing backup directory to match the new email address,