501 5.5.2 RCPT TO syntax error
The destination email address is invalid according to the RFC 2822 Internet message format standard.
Note:
Some systems allow addresses that are not fully compliant with the standard.
A typical example is an email address whose local-part begins or ends with a ‘.’ (dot, period or full stop) character. This is not allowed by the standard. Some receivers may, however, choose to accept these addresses by ignoring the additional character, or using it as a component of the unique local-part.
SmartRelay enforces the standard and refuses to accept an email sent to an invalid address. This behavior can, however, be changed if required.
This is a permanent error. Re-sending the message will not succeed unless the recipient address is corrected.
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