Caller: Scammer claiming to be Telstra

Called claiming to be Telstra, listened because they weren't asking for any personal details (already had my name). They asked me to confirm a code sent to my phone and noticed the code was sent from old email provider - they were trying to log into my email but didn't realise it was an old account I don't use (not linked to Telstra). Don't know what they were trying to access my email for, but could have been bad if they had gotten access to an email account actually used. Don't know how they had my old email - haven't used that for almost a decade.