IOS – How to disable an email account when the password has changed

In Mail 9 (el capitan) this is done by adding the new address as an "Alias" in the Preferences.

Mail > Preference > Accounts tab > Account information tab. Above the "Email address" Field you will see "Alias". Click, and click "edit Alias". Click the plus (+) icon on the bottom left, and add the email address and name.

Of course the address must be properly set up and authorised as an extra account in the Gmail interface itself first.

Gmail > Settings > Accounts and Import > Send mail as. Treat as alias must be on (checked).

There are few ways to do this.

My Preferred way is::

Move all mails and folders you want to keep to "On My Mac" location.

Then in Mail app open Preferences--Accounts.

Uncheck the "Enable this Account"

It is now deactivated, but you still have the copies of the emails in your "On my Mac" location.

Sorry, the instructions are for 10.9.5.

As you will see the account is still there but grayed out, thus you can reactivate at any time.