Have lost mail and can't reload it

What model and year is your Mac? See that you are running El Capatan. Maybe updating to Sierra would solve the issue?

How to get macOS Sierra - Apple Support

Let me know if you need more help. Here all afternoon online. 😀 😎

Hi there,

I would try signing out of iCloud on your Mac, and then sign right back in. This will refresh the iCloud Mail Client and settings associated with your device and usually resolves any mail issues.

Things to check also -

System Preferences > iCloud > Make sure Mail has a check next to it

Mail > Preferences > Accounts > Make sure iCloud is enabled

Hi!

Go up to the  > System Preferences > iCloud

- you should see on the left the option to sign out

When signing back into iCloud, if it's asking you to update your iCloud password go ahead and do so. Sometimes this happens if you haven't updated or changed the password in a while.

It's likely you are using the iCloud/Apple ID password to log into your user on the computer (are they the same password?)

If they are, it's basically asking you to create another user log in password since you're signing out of iCloud. (the computer is assuming that you're removing your iCloud account, so it needs you to create a new user password to get into the computer) You can confirm this by:

 > System Preferences > Users & Groups > Click the little lock on the bottom left to enter your computer password and unlock > You should see a "change password" option > click on Change Password and it should tell you if you're using an iCloud Account Password to unlock your Mac or not.

I would just put in the same password you've been using to avoid confusion.

Yes, you're essentially telling the computer to no longer use the iCloud password as the login password for the computer.

1. Go to System Preferences > User & Groups > Change Password > "Use Separate Password"

- this will have you confirm your iCloud password and then create a computer password (again, I would just use the same one you're used to to avoid confusion) > Done.

2. System Preferences > iCloud > Sign Out of iCloud

- this will ask you to delete or remove content as it's signing out, but select "keep" on any data it allows you to (it's quicker than removing it)

- "delete" is a scary word, but we're basically taking iCloud data off when we sign out and then putting it back on once we sign back in (it's not lost!)

3. Sign back into iCloud > make sure Mail (and everything else you use) is enabled/has a check mark.