It depends on how you choose to send the file.
6-digit key Transfer
Instead of keeping the file on the server, the file will be sent to the other party instantly.
Files shared with a share-link are kept on the server for up to 48 hours.
If you upgrade Send Anywhere PLUS, you can set expiration time as you want.
And it will be deleted after the expiration date or user deleted a share-link. All the files get deleted from the server once it expires for security reasons. After then it cannot retrieve anymore.
To Device Directly
Files sent to a device are kept on the server for up to 48 hours. When the other party receives the file, the file is deleted automatically from the server and will be deleted from the server after 48 hours, even if the file is not received.