From your iPhone or iPad you can install a profile for the Apple mail app to use to access your mail.coop account. Here’s how.
Visit https://mail.mail.coop
Log in using your mail.coop username (for example myname@myphone.coop) and password.
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Having logged in you will see options
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Select ‘General’
You will see the General configuration page. This is where you can do things like change your password.
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Scroll down to section headed “Apple connection profile with app password”. Then select ‘Email’ link where it says ‘Apple connection profile with app password’
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You will see a dialog box
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Select Allow on the dialog box. You will see a notice saying it has downloaded.
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You can close this and go to Settings. There will be a new item near the top: ‘Profile Downloaded’.
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Select ‘Profile Downloaded’
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Select ‘Install’ top right.
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Select ‘Install’ again. It’s OK that the profile is not signed
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And select ‘Install’ again!
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You’ve done it! Select ‘Done’.
Then go to the Mail app and you will find a new account for your new mail.coop mailbox.