The file could be corrupt, or...
There are two kinds of SQL Anywhere backups.
99.999% of SQL Anywhere backups are made using the "image backup" type.
The remainder (i.e., almost none) are made using the "archive backup" type which was originally designed for tapes.
Judging by the message you got, the email probably contained an image backup.
Restoring an image backup requires zero effort, other than unzipping it and copying the file to the desired location, and running dbsrv17. No RESTORE command required.
The Help really should contain "DON'T USE THIS COMMAND!" in the section on RESTORE : )
