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SMTP Error 500

Category: Other
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Description: Syntax error, command unrecognized (This may include errors such as command line too long).

What does this mean?

The receiving SMTP mail server was unable to correct process the command(s) received. Also note, commands that are processed but not used will be handled with different response numbers.

How to fix SMTP Error 500?

The unrecognized command response is typically in regards to antivirus or firewall software. To confirm if this is the case, temporarily disable each one, re-instating them if not the area of concern.

SMTP Error 500 Examples

SMTP Permanent Error: 500 Access Denied By Port Access
SMTP Error 500 Line too long