Thank you. I'll look into this and make the necessary corrections.
Appreciate the help.
Update: Found an email account in my macbook I configured back when HelioHost was still using CPanel. This is probably the one causing the failed IMAP login issue. The email account uses a subdomain that does not work anymore in Plesk (I didn't bother to request a CNAME record for this subdomain to be added during the Plesk migration). Anyway, I've removed this email account in my mail client so hopefully, the IMAP login failures will now be gone.