Email settings cannot be saved

‘How to do a IMAP setting on port 993 & SMTP at 465’

So there are the email setup instructions to check for help https://frappe.github.io/erpnext/user/manual/en/setting-up/email/email-account

Otherwise to troubleshoot, the idea is divide and conquer in steps, to confirm what does and doesn’t work to isolate the problem - here are some checks to try