I administrate an Exchange server for a customer, and now the (transaction?) logs are taking up massive amounts of space.
Are they safe to delete?
The logs are taking ~70GB of space, while the database itself is only ~8GB.
Are they safe to delete? NO. ABSOLUTELY NOT.
Exchange transaction logs contain records of actions taken on the mail store (including email data) and this data is supposed to be committed to the main database when time permits, and the logs tidied up after a successful full 'exchange aware' backup.
Just deleting them is a great way to lose data; instead you need to investigate why they're not being managed as part of the normal operation of that exchange server. This problem suggests at the very least that backups are not taking place, or possibly that a worse problem exists.