Bad Backup, Emails Emigrated

fbjon writes: Just before Christmas, one of Swedish broadband provider Telia's central mailservers started going wonky, and finally crashed and burned on the 3rd of January. Fortunately, backups are taken regularly. Unfortunately for 300.000 customers, all backups since the 15th of December are unreadable, and cannot be salvaged. The number of mails lost is unknown. All affected customers will receive an email, as well as a 200 euro gift card as compensation.

When did you last verify your backups?