Documentation for Alerting Email Action Could Use Updating

[mark54g]

Kibana version:
7.10.1

Elasticsearch version:

Server OS version:

Browser version:

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug:
Every example listed here: https://www.elastic.co/guide/en/kibana/7.10/email-action-type.html#configuring-email mentions the secure option, and should reflect what the toggle to off would do better (in some cases, it's necessary to disable secure for the initial connection, and a secure connection will be established if the provider requires it).

For example when going to the nodemailer docs for that you get this important detail:

if true the connection will use TLS when connecting to server. If false (the default) then TLS is used if server supports the STARTTLS extension. In most cases set this value to true if you are connecting to port 465. For port 587 or 25 keep it false

This is especially true with o365 email, as it uses port 587, but should possibly or even probably not have secure enabled when using it with Kibana Alerts.

Also appears that the Outlook example may be dated in the docs, per:
https://support.microsoft.com/en-us/office/pop-imap-and-smtp-settings-for-outlook-com-d088b986-291d-42b8-9564-9c414e2aa040

Steps to reproduce:
N/A - Documentation update request

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[pmuellr]

Looking at the email docs, I can see we added the examples in this PR, where some of the values came from watcher docs - #69601 (comment) . Those may be slightly out-of-date (eg, the outlook one seems to have changed).

The values that nodemailer uses, when you just pass a "service" name, are here: https://github.com/nodemailer/nodemailer/blob/master/lib/well-known/services.json - I think we may want to link to this file in the connector doc, somehow. I often refer people to it ...