This error typically indicates that the "From" email address does not match the SMTP username.
It may be commonly visible when using third-party plugins that use their email addresses by default to send emails, and in these instances, the email address will not match the SMTP username.
The user may need to ensure that the "From" email address matches the SMTP username to resolve this issue. The default parameters may not force this setting; in these cases, the user may need to add the required configuration to force the email address to match the SMTP user name.
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