As an anti-spam measure, mail servers have implemented a "Sender Address Verification" or "Callback Verification." If the mail server is unable to verify the sender's address, it will reject the email with the error message '550 Sender verify failed'.This article discusses why '550 Sender verify failed' messages may occur when you try to send e-mail, and how to resolve the issue.
When you try to send an e-mail message, you receive the following SMTP error message:
550 Sender verify failed
This error message occurs when the sender e-mail account does not exist in cPanel, or when the domain's MX entry records are misconfigured in cPanel.
For example, suppose you add a parked domain, an addon domain, or even an entire cPanel account (if you are a reseller). If the domain's MX records (as set at the domain registrar) point to an external e-mail provider, you must also configure the MX entries in cPanel to use the external e-mail provider. Additionally, in cPanel you must create the e-mail accounts that you want to use to send messages.
To resolve this issue, follow these steps:
Make sure the domain is configured to use the remote e-mail provider.
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