I am using both EmClient and Outlook and when I delete an email in EC it is also deleted in Outlook. I need this to stop and don’t know what to do.
That’s probably because you are using a protocol that syncs with the server-- either IMAP or exchange. This is their design and there is no way to change this using these protocols. You can use the POP3 protocol, which only downloads messages to your eM Client inbox and does not sync with the server, Therefore, anything you do in eM Client will not be replicated to the server or other clients.
You can’t change the protocol, you must setup the account again and then delete the old account. To do this, when you add the account, do not use the automatic setup. Click on “Mail” and then “Other”. You can then set up the account as POP3. You will need to get the server settings from your email provider.