Mail App, People App and Calendar App

I posted this question in the mail section; maybe the wrong section as I got 0 replies; sorry for that.

I am using Mail App, People App and Calendar App on my Microsoft Windows Home Edition 20H2 OS.
In Mail I have 3 accounts: an Outlook.com account, an iCloud.com account and a local provider account: Telenet.be
all works fine in Mail App but in People App and Calendar App when I open settings (gear icon) I only see 2 accounts (Outlook.com and iCloud.com); adding a third account leads to error: 0x80004005
Can anyone help me with that problem please?

another additional question: in the settings of my telenet.be account I see (automatically added with the creation of the mail account)
for incoming email server: imap.telenet.be:993:1
for outgoing email server: smtp.telenet.be:587:0

I think the numbers 993 an 587 are port numbers but I have no idea (nor can't find) what the numbers 1 and 0 mean.
Has someone an explanation please?

thanks in advance, gabriël

The correct settings for Telenet in Mail app of Windows 10 are shown here:
E-mailprogramma instellen voor je Telenet e-mailadres
(It may take a while before it loads to step 8 near the bottom of the page.)

You are correct about port numbers, no idea what the 0 or 1 means, it occurs on some of my accounts after the port number, but it is auto added as are the servers.

The reason the People App and Calendar App not working maybe that the account does not have the facility or some format incompatibility.

My ISP Email account is like that, Mail only, no Sync option for Calendar/Contacts.

Outlook/Gmail/Yahoo all have the Calendar/Contacts options.

thank you very much for your answers.
much appreciated, gabriël