Mac OS Mail - Cannot send the message using the server iCloud
I'm unable to send emails from my iCloud account though receive them fine.
When sending a message I get a dialogue box titled "Cannot send the message using the server iCloud" with the following:
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Verify that you have addressed this message correctly. Check your SMTP server settings in Mail preferences and verify any advanced settings with your system administrator.
The server response was: <unknown[58.174.60.140]>: Client host rejected: Access denied
Select a different outgoing mail server from the list below or click Try Later to leave the message in your Outbox until it can be sent.
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I get the option to select a different outgoing server, 1 is iCloud and although it shows it can't be selected, the other is my internet providers server and while this lets the email send the message gets quarantined by their mail systems.
I've been through the support articles but none have been able to help so any help would be appreciated.
Cheers
iMac Pro, macOS 13.4