The SMTP Error 501 is associated with syntax issues in the parameters or arguments of the SMTP command being used. Essentially, when you’re trying to send an email, there might be a mistake or misconfiguration in how the command is structured or its parameters.
As a result, the mail server identifies this inconsistency and returns the error. Such issues could stem from incorrect email formatting, a missing domain in the address, or unsupported characters in the email’s subject or body.
Resolving the Error – Solution
To address the SMTP error 501:
- Ensure the email address you’re sending to follows a format like ‘[email protected]’.
- Check if there are any odd or special characters in your email’s subject or body. Remove them if present.
- Ensure the sender’s email address is properly formatted, with the local part (before the ‘@’ sign) between 1 and 64 characters, and the domain (after the ‘@’ sign) no more than 255 characters.
- Some software, like antivirus or firewall programs, may interfere with the sending process. Try temporarily disabling them and see if the error resolves. If the problem is not with them, turn them back on.