This depends on the transmission method used.
6-digit Key Transfer
Instead of storing files on the server, files are instantly sent to the recipient.
By default, files uploaded to a share link are kept on the server for up to 48 hours. However, Send Anywhere Email Add-on subscribers can set a download expiration date, allowing the files to remain on the server for the designated period. Once the link creator deletes the link or the link expires, all the files get permanently deleted from the server.
Directly To Device
Sent Files are kept on the server for up to 48 hours. If the other party receives the files, they are deleted automatically from the server, and if they don't, they will be deleted from the server after 48 hours.
※ All methods except share-link are 1:1 one-time transfers.
※ For security purposes, once deleted from the server, it cannot be recovered again.