Nah you can use ghetto smtp to relay incoming mail to a different port on your server if your ISP blocks incoming 25 and sendinblue (it’s changed names but my sendinblue config is still working) to send outgoing mail if they block outgoing 25. It’s less than ideal but doable for low volume private email servers.
Most ‘hackers’ are just mid tier (mediocre) IT level types who rely on existing exploits floating around in the wild. It’d probably be hard to find any still in circulation for such an old system.