They are, and the legal definition of a backup is provided in the legislation. While you do not have right of access to a backup record under DP legislation, they are within the remit of the legislation and the Data Protection Commissioner has treated backups in both guidelines and decisions. Also the DP legislation is not irrelevant to this case. If the e-mails contain personal information, the friend is arguably a data processor and possibly a data controller within the meaning of the Acts and therefore had certain legal responsibilities related to this role.