Code	Enh. Code	Message	Description	Action
500	5.5.1	Command unrecognized	The SMTP command currently used was unrecognized or is not supported by VisNetic MailServer.	Review the syntax of the last command and try again. Another possibility is that you are trying to use telnet and the telnet connection to your server is not allowed. Check the Admin console - Mail service - Security - Protocols.
501	5.5.2	Domain name required	Sender has no domain specified (usually in MAIL FROM)	Specify the senders' domain name and try again. The problem may be in your e-mail client, not VisNetic MailServer. If your e-mail client is not properly configured with a domain name this could happen.
501	5.5.2	Unbalanced	SMTP session syntax invalid. (usually unbalanced brackets)	Check the syntax of the last command and the configuration of various DAT files.
501	5.5.4	Syntax error in parameters scanning	Common syntax error. You probably mistyped last command or last string is invalid.	Check the syntax of the last command.
501	5.5.1	HELO/EHLO requires domain address	Usually when there was blank or invalid string sequence after HELO/EHLO command.	Greet VisNetic MailServer again with correct HELO/ELHO command.
501	5.0.0	Authentication cancelled	The process of authentication was cancelled for any reason.	Restart the authentication process by using proper command.
501	5.7.0	Authentication failed	The username/password combination provided during authentication was invalid.	Reenter both the username and the password and authenticate again.
501	5.7.1		You are not allowed to send.	Be sure "Reject if no rDNS" is NOT checked in VisNetic MailServer Admin console or Put the local IP range and your email client program IP in the "Relaying from" box.
502	5.5.1	Sorry, we do not support this operation	This operation is not allowed.	You can allow/disallow particular operations and commands from the VisNetic MailServer Admin console - SMTP - Security node - Protocols.
503	5.5.1	Incorrect command sequence	A supported command was issued out of sequence. For example command RCPT TO used before MAIL FROM or DATA command used when RCPT TO command was not accepted.	Solution depends on the situation where this error occurred. Check last few commands sequence.
503	5.5.1	Authentication already done	Error occurs by re-authentication.
503	5.5.1	HELO/EHLO command required	Greeting error. HELO/EHLO command is required.	You have to use HELO or EHLO command. You can specify this option in VisNetic MailServer Admin console - SMTP - Security - Protection tab.
503	5.5.1	HELO/EHLO already specified	Greeting used again.
504	5.7.6	Unrecognized authentication type	Invalid authentication type. Incorrect or none type of AUTH specified.	Use the command AUTH with proper authentication type.
530	5.7.1	Authentication required [AUTH]	Authentication with command AUTH is required.	Use AUTH command or enable/disable authentication obligation from your VisNetic MailServer Admin console.
550	5.7.1	We do not relay	Server is not open for relay.	Read this Article.
550	5.7.1	We do not relay, account limits apply		Check the account limits for the particular user account and whole domain.
550	5.7.1	You have rights to send mail to local domains only	The user who gets this error is allowed to send mail only to local domains.	There is a checkbox in VisNetic MailServer Admin Console, user account management - Mailbox tab. Enable or disable it.
550	5.7.1	Access not allowed	1)VisNetic MailServer is blocking access by a black list filter. or 2) Reject if originator's domain is local and not authorized option turned on. or 3) Sending to a mailing list set to members only.	1) Review VisNetic MailServer B&W filter settings or set a bypass file. 2) Local users have to be authorize before sending mail, this set up is in their email client, POP before send, use SMTP Authentication or Allowed relay IP. 3) Add your sender address to the mailing list you are sending to.
550	5.7.1	Permission denied
550	5.1.1	Unknown user local
550	5.1.1	Unknown user; rejecting	Unknown user account. The recipient is not local, thus reject the message.	Behaviour and the treatment of messages coming to unknown user accounts can be set from VisNetic MailServer admin console - domain management - domain tab.
551	5.1.1	No such user found	User account is not local.
551	5.1.1	No such mailing list found	Mailing list is not local.
552	5.5.3	Too many recipients	The number of recipients exceeds the maximum of allowed recipients.	Older versions of VisNetic MailServer used to follow RFC and had maxium of recepients set to 100. If you need more recipients, use mailing lists or download the latest version of VisNetic MailServer (support for unlimited number of recipients added).
554	5.3.4	Message size exceeds fixed maximum message size	Too much data was sent by the user. User account has an amount limitation.	You can increase or disable amount limit from VisNetic MailServer Admin console - user account management - mailbox tab. Make sure all 3 levels (server, domain and user) are set to 0. (for unlimited)
554	5.7.1	Message cannot be accepted, virus found	Virus was found in the message body or in the message attachment.
554	5.7.1	Message cannot be accepted, content filter rejection	Content filter applied and the message was rejected.	Review the content filter settings in the VisNetic MailServer Administration console.
554	5.7.1	Message cannot be accepted, spam filter rejection	Message is probably spam.	If you do not think this message is spam, try to alter the configuration of the VisNetic MailServer Instant Anti-spam engine. Or review your Black and White list filters for sender rejection
		Message deleted by filter		Alter your filter configuration. Usually Challenge Response or Black and White list in Webmail or VisNetic MailServer Admin
		Message challenged by filter		Challenge Response can be disabled in the VisNetic MailServer Anti-spam settings (Challenge Response tab)
554	5.2.2		Maximum size exceeded.	Check global settings, domain options and user mailbox settings. Webmail also has a max message size. Log on to Webmail, Settings, Administrator Settings.
554	5.3.1		Maximum message size exceeded.
554	5.7.1	Message cannot be accepted, filter rejection	The message was rejected.	Check your filters settings and configuration.