El Capitan Apple Mail.app Passwords Won't Take

Actually, it's not working. Accounts keep refusing the passwords.

I've got Mail.app closed and into System Preferences::Internet Accounts and I just deleted my account, and re-created it. It still says Unable to verify account name or password.

Now what should I do?

Cheers

Just deleted the full account, both in Mail.app and System Preferences::Internet Accounts.

Started fresh. SP::IA tried with my account info and it still says "Unable to verify account name or password." Webmail works. Nothing has changed.

Why is OSX not working? Console on internetaccounts:

2020-09-01 7:32:04.815 AM com.apple.preferences.internetaccounts.remoteservice[889]: Unable to simultaneously satisfy constraints:
(
    "<NSLayoutConstraint:0x7ff18dca9850 H:[NSView:0x7ff18dc1bc60(405)]>",
    "<NSLayoutConstraint:0x7ff18b7153f0 H:|-(0)-[NSView:0x7ff18dc1bc60]   (Names: '|':NSView:0x7ff18dc01b30 )>",
    "<NSLayoutConstraint:0x7ff18dc28870 H:[NSView:0x7ff18dc1bc60]-(0)-|   (Names: '|':NSView:0x7ff18dc01b30 )>",
    "<NSLayoutConstraint:0x7ff18dcaff20 H:[NSView:0x7ff18dc01b30(407)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7ff18dca9850 H:[NSView:0x7ff18dc1bc60(405)]>

Set the NSUserDefault NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints to YES to have -[NSWindow visualizeConstraints:] automatically called when this happens.  And/or, break on objc_exception_throw to catch this in the debugger.
2020-09-01 7:32:04.816 AM com.apple.preferences.internetaccounts.remoteservice[889]: Unable to simultaneously satisfy constraints:
(
    "<NSLayoutConstraint:0x7ff18dc45960 V:[NSView:0x7ff18dc1bc60(197)]>",
    "<NSLayoutConstraint:0x7ff18dc30090 V:|-(0)-[NSView:0x7ff18dc1bc60]   (Names: '|':NSView:0x7ff18dc01b30 )>",
    "<NSLayoutConstraint:0x7ff18dc1d500 V:[NSView:0x7ff18dc1bc60]-(0)-|   (Names: '|':NSView:0x7ff18dc01b30 )>",
    "<NSLayoutConstraint:0x7ff18dcab510 V:[NSView:0x7ff18dc01b30(301)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7ff18dc45960 V:[NSView:0x7ff18dc1bc60(197)]>

Set the NSUserDefault NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints to YES to have -[NSWindow visualizeConstraints:] automatically called when this happens.  And/or, break on objc_exception_throw to catch this in the debugger.
2020-09-01 7:32:08.495 AM com.apple.preferences.internetaccounts.remoteservice[889]: Error in CoreDragRemoveTrackingHandler: -1856
2020-09-01 7:32:08.495 AM com.apple.preferences.internetaccounts.remoteservice[889]: Error in CoreDragRemoveReceiveHandler: -1856


Found a mail log:

Sep  1 07:57:15  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Disconnected]> Read: * OK [CAPABILITY (
	    IMAP4REV1,
	    STARTTLS,
	    "AUTH=PLAIN",
	    "AUTH=LOGIN"
	)]
Sep  1 07:57:15  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 1.32 STARTTLS
Sep  1 07:57:15  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 1.32 OK
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 2.32 CAPABILITY
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: * CAPABILITY IMAP4REV1 AUTH=PLAIN AUTH=LOGIN
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 2.32 OK
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 3.32 AUTHENTICATE PLAIN
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: +
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 3.32 BAD Authentication aborted by client.
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 4.32 AUTHENTICATE PLAIN
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: +
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 4.32 BAD Authentication aborted by client.
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 5.32 AUTHENTICATE LOGIN
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: +
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 5.32 BAD Authentication aborted by client.
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 6.32 AUTHENTICATE LOGIN
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: +
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Read: 6.32 BAD Authentication aborted by client.
Sep  1 07:57:16  Mail[1757] <Debug>: <0x7fafcc6f09c0:[Non-authenticated]> Wrote: 7.32 LOGOUT

Seems this fine application (whose rules never work) can't even authenticate. The account is just fine.

Hosting provider had a security breach and didn't tell me. Passwords reset, all is good.

Cheers

Actually everything is working now. Multiple restarts and placing passwords in System Preferences::Internet Accounts as well as Mail.app::Preferences::Accounts eventually worked.

Cheers