How the change the registered lifetime plex pass email account?

I have my Plex registered to an email account that Microsoft retired (@msn.com).
I want to change it to @outlook.com.
In the account settings on the Plex Server I am unable to do this.
How can I fix it?

Take down any 3rd-party scripts or apps which are accessing your Plex account.
Your account was constantly under temporary lockdown due to excessive amounts of access attempts. Hint: predominantly during night time)

It is very likely that this is the reason why you couldn’t change your email.
Switch off any of these foreign accesses and wait at least 12 hours. Then try again.
Hint: switching from one Microsoft-owned domain to another will not improve the situation regarding email from Plex. Apparently Microsoft has some undisclosed policies in place which either are deleting, or significantly delaying delivery of email from plex.tv

Ok, I will give it a try. I am however unable to acces my @msn.com account.
So where do I find the 3rd party apps? Is this like Xplay and such?

You won’t need access to the old email account. You need only the right Plex password.
Use the hosted web app: https://app.plex.tv/desktop/#!/settings/account

Something like “Home Assistant” or “Tautulli” are typical 3rd-party apps with access to your plex account.
Yes, Xplay is also a 3rd-party client.