Interpretation of 5xx Errors in Icewarp SMTP

Code	En. Code	Error Phrase	Description	Remedy Instructions
500	5.5.1	Command unrecognized	The SMTP command currently used was unrecognized or is not supported by the SMTP service.	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 settings in administration console: Mail Service - Security - Advanced.
501	5.5.2	Domain name required	Sender has no domain specified (usually in MAIL FROM).	Specify the sender's domain name and try again. The problem will be with user's email client, not your server. The email client configuration is probably not supplied with a domain name.
501	5.5.2	Unbalanced	SMTP session syntax invalid (usually unbalanced brackets).	Check the syntax of the last command and the configuration of corresponding .dat files.
501	5.5.4	Syntax error in parameters scanning	Common syntax error. You probably mis-typed 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.	Retry the SMTP greeting with correct HELO/ELHO command.
501	5.0.0	Authentication canceled	The process of authentication was canceled for any reason.	Restart the authentication process by using proper command.
501	5.7.1	Message is too long	Exceeded message size limit	Review settings of limits on server/domain/user levels.
501	5.7.1	Permission denied	1) Username given in AUTH differs from sender in mail FROM 2) Message submission is active and not used by local sender, or unauthenticated access to submission port 3) Milter filter returns error in envfrom stage	1) Disable this - check in administration console: Mail - Security - Advanced - Reject if SMTP AUTH different from sender. 2) Local senders has to use submission port or disable this setting using the C_Mail_SMTP_Delivery_MessageSubmission API variable. 3) Check used filter.
501	5.7.1	Sender domain must exist	MX record of sender's domain was not found	Disable this - check in administration console: Mail - Security - DNS - Reject if originator's domain doesn't exist or disable the C_Mail_Security_Protection_RejectMX API variable.
501	5.7.1	Sender IP must resolve	Reverse DNS query on sender's IP failed	Disable this - check in administration console: Mail - Security - DNS - Reject if originator's IP has no rDNS or disable the C_Mail_Security_Protection_RejectrDNS API variable.
501	5.7.1	Sender refused by the DNSBL	Sender's domain was blacklisted by DNSBL server	Check used DNSBL server or you can disable this feature in administration console: Mail - Security - DNS - Use DNSBL or by the C_Mail_Security_Protection_DNSBL API variable.
501	5.7.1	Soft quota applied	Mail sending blocked	When the quota is exceeded, the user still can receive mails as normally, but each attempt to send mail will fail.
502	5.5.1	Sorry, we do not support this operation	This operation is not allowed.	You can allow/disable particular operations and commands from the administration console: Mail Service - Security - Advanced.
503	5.5.1	Incorrect command sequence	A supported command was used in invalid order. For example command RCPT TO used before MAIL FROM or DATA command used when RCPT TO command was not accepted.	Solution depends on the context in which this error occurred. Check the 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 by the server.	You have to use HELO or EHLO command. You can deactivate this option in administration console, or create a Bypass: Mail Service - Security - Advanced.
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 (SMTP Server requires authentication) or disable this authentication type in administration console.
535	5.7.1	Authentication credentials invalid	1) The username/password combination provided during authentication was invalid. 2) Milter filter auth action	1) Re-enter both the username and password and authenticate again. 2) Check used filter.
550	5.1.1	User unknown; rejecting	1) Recipient's domain is set to reject unknown accounts 2) User was not found on other servers in a distributed domain	1) Review setting of Domain - Options - Unknown accounts - Action. 2) Check other servers in your distributed domain for given account.
550	5.1.1	User %s has invalid forward set and no mailbox; rejecting	It is returned, when somebody is trying to send a mail to a user, who has NULL mailbox and non of their forwards is valid. (Then the mail is undeliverable).
550	5.7.1	Access to recipient not allowed [SPF-SRS]	SRS hash check failed for received NDR	You can disable this security check in Mail - Security - DNS - Use SRS NDR Validation or via the C_Mail_SMTP_Other_SPFSRSNDRVerify API variable.
550	5.7.1	We do not relay	Server is not open for relay.	Refer to this FAQ.
550	5.7.1	We do not relay, account limits apply		Check the account limits for the particular user account, its domain and on the server level.
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.	Disable this option in the administration console: Management - <User> - Options - User can send mail to local domains only.
550	5.7.1	Access not allowed	1) Server blocked access by a blacklist filter, or 2) Reject if originator's domain is local and not authorized option turned on.	1) Review server black list filter settings or set a bypass file. 2) Local users have to authorize themselves so if they do not have this set up in their e-mail clients and you turned this on they are not allowed to send.
550	5.7.1	Access to not allowed by rules	1) Server blocked user access by a blacklist filter/rule, or 2) Server blocked access from the originating server by HELO/EHLO Filter.	1) Review server black list filters and user rules or set a bypass item. 2) Whitelist the originating server in HELO/EHLO filter, or remove it from blacklist, or create a Bypass.
550	5.7.1	Permission denied
550	5.1.1	Unknown local user
550	5.1.1	Unknown user; rejecting	Unknown user account. The recipient is not local, thus reject the message.	Behavior and the treatment of messages coming to unknown user accounts can be set from administration console: Management - <Domain> - Options - Unknown Accounts.
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	5.2.2	Mailbox has exceeded the limit	Recipient's mailbox is full and C_Mail_SMTP_Other_FullMailboxPermanentError has been set.	Check recipient's quota on server/domain/user levels.
554	5.3.4	Message size exceeds fixed maximum message size	Too many data was sent by the user. User account has an amount limitation.	You can increase or disable amount limit from administration console - Management - <User> - Limits tab. Make sure all 3 levels (server, domain and user) are set to 0 (stands for unlimited).
554	5.7.1	Permission denied	1) Access restriction to all services is enabled and sender's IP address was found in denied list. 2) User sent some data before greeting from server was sent. 3) Milter filter returns error in connect stage.	1) Check service's access list in System - Services - <Service> - Properties - Access or disable the C_System_Services_Firewall API variable
554	5.7.1	Message cannot be accepted, rules rejection	1) Sender is blacklisted. 2) External filter rejects the message. 3) Milter filter returns error in eom stage.	1) Check system and recipient's blacklist. 2) Check used external filters. 3) Check used external filters.
554	5.7.1	Message cannot be accepted, virus found	Virus was found in the message body or in the message attachment.	If you think the attachment is not harmless (false positive), try to alter the configuration of the antivirus engine (Quarantine instead of Reject), or create a Bypass entry.
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 administration console.
554	5.7.1	Message cannot be accepted, spam filter rejection	Message is probably spam.	If you think this message is spam (false positive), try to alter the configuration of the Antispam engine, index the message by Bayesian or create a blacklist entry.
554	5.7.1	Message cannot be accepted, spam rejection	Message is probably spam.	If you think this message is not spam (false positive), try to alter the configuration of the Antispam engine, index the message by Bayesian or create a whitelist entry.
		Message deleted by filter		Alter your content filters configuration.
554	5.7.1	Message cannot be accepted, filter rejection	The message was rejected.	Check your filter settings and configuration.
554	5.7.1	Permission denied. Maximal parallel connections from this IP reached	Number of connections coming from particular IP address exceeds the limit of maximal number of parallel connections.	Click the Bypass button in intrusion prevention settings (SMTP specific rules) to specify an IP address (or a range of IP addresses), where this limit is not applied. Or increase the value of c_mail_smtp_general_parallelipconnectionslimit variable. Zero means no limit.
554		Could not connect and send the mail to recipient	Client session - target server not responding	Check target server.
554		Could not verify SSL connection	Client session - target server SSL certificate cannot be verified	Check target server.
554		Permanent problems with the remote server	Client session - server returned 4xx or 0xx status	Try again later.
554		... while issuing MX query	Client session - cannot obtain MX for target server	Check DNS
554		Could not resolve target DNS	Client session - cannot contact DNS	Check DNS
554		Too many hops	Message was redirected by more than C_Mail_SMTP_Other_MaxHopCount SMTP servers	Check mail delivery path recorded in the Received headers.

500

5.5.1

Command unrecognized

The SMTP command currently used was unrecognized or is not supported by the SMTP service.

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 settings in administration console: Mail Service - Security - Advanced.

501

5.5.2

Domain name required

Sender has no domain specified (usually in MAIL FROM).

Specify the sender's domain name and try again.

The problem will be with user's email client, not your server. The email client configuration is probably not supplied with a domain name.

501

5.5.2

Unbalanced

SMTP session syntax invalid (usually unbalanced brackets).

Check the syntax of the last command and the configuration of corresponding .dat files.

501

5.5.4

Syntax error in parameters scanning

Common syntax error. You probably mis-typed 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.

Retry the SMTP greeting with correct HELO/ELHO command.

501

5.0.0

Authentication canceled

The process of authentication was canceled for any reason.

Restart the authentication process by using proper command.

501

5.7.1

Message is too long

Exceeded message size limit

Review settings of limits on server/domain/user levels.

501

5.7.1

Permission denied

1) Username given in AUTH differs from sender in mail FROM

2) Message submission is active and not used by local sender, or unauthenticated access to submission port

3) Milter filter returns error in envfrom stage

1) Disable this - check in administration console: Mail - Security - Advanced - Reject if SMTP AUTH different from sender.

2) Local senders has to use submission port or disable this setting using the C_Mail_SMTP_Delivery_MessageSubmission API variable.

3) Check used filter.

501

5.7.1

Sender domain must exist

MX record of sender's domain was not found

Disable this - check in administration console: Mail - Security - DNS - Reject if originator's domain doesn't exist or disable the C_Mail_Security_Protection_RejectMX API variable.

501

5.7.1

Sender IP must resolve

Reverse DNS query on sender's IP failed

Disable this - check in administration console: Mail - Security - DNS - Reject if originator's IP has no rDNS or disable the C_Mail_Security_Protection_RejectrDNS API variable.

501

5.7.1

Sender refused by the DNSBL

Sender's domain was blacklisted by DNSBL server

Check used DNSBL server or you can disable this feature in administration console: Mail - Security - DNS - Use DNSBL or by the C_Mail_Security_Protection_DNSBL API variable.

501

5.7.1

Soft quota applied

Mail sending blocked

When the quota is exceeded, the user still can receive mails as normally, but each attempt to send mail will fail.

502

5.5.1

Sorry, we do not support this operation

This operation is not allowed.

You can allow/disable particular operations and commands from the administration console: Mail Service - Security - Advanced.

503

5.5.1

Incorrect command sequence

A supported command was used in invalid order. For example command RCPT TO used before MAIL FROM or DATA command used when RCPT TO command was not accepted.

Solution depends on the context in which this error occurred. Check the 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 by the server.

You have to use HELO or EHLO command. You can deactivate this option in administration console, or create a Bypass: Mail Service - Security - Advanced.

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 (SMTP Server requires authentication) or disable this authentication type in administration console.

535

5.7.1

Authentication credentials invalid

1) The username/password combination provided during authentication was invalid.

2) Milter filter auth action

1) Re-enter both the username and password and authenticate again.

2) Check used filter.

550

5.1.1

User unknown; rejecting

1) Recipient's domain is set to reject unknown accounts

2) User was not found on other servers in a distributed domain

1) Review setting of Domain - Options - Unknown accounts - Action.

2) Check other servers in your distributed domain for given account.

550

5.1.1

User %s has invalid forward set and no mailbox; rejecting

It is returned, when somebody is trying to send a mail to a user, who has NULL mailbox and non of their forwards is valid. (Then the mail is undeliverable).

550

5.7.1

Access to recipient not allowed [SPF-SRS]

SRS hash check failed for received NDR

You can disable this security check in Mail - Security - DNS - Use SRS NDR Validation or via the C_Mail_SMTP_Other_SPFSRSNDRVerify API variable.

550

5.7.1

We do not relay

Server is not open for relay.

Refer to this FAQ.

550

5.7.1

We do not relay, account limits apply

Check the account limits for the particular user account, its domain and on the server level.

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.

Disable this option in the administration console: Management - <User> - Options - User can send mail to local domains only.

550

5.7.1

Access not allowed

1) Server blocked access by a blacklist filter, or

2) Reject if originator's domain is local and not authorized option turned on.

1) Review server black list filter settings or set a bypass file.

2) Local users have to authorize themselves so if they do not have this set up in their e-mail clients and you turned this on they are not allowed to send.

550

5.7.1

Access to not allowed by rules

1) Server blocked user access by a blacklist filter/rule, or

2) Server blocked access from the originating server by HELO/EHLO Filter.

1) Review server black list filters and user rules or set a bypass item.

2) Whitelist the originating server in HELO/EHLO filter, or remove it from blacklist, or create a Bypass.

550

5.7.1

Permission denied

550

5.1.1

Unknown local user

550

5.1.1

Unknown user; rejecting

Unknown user account. The recipient is not local, thus reject the message.

Behavior and the treatment of messages coming to unknown user accounts can be set from administration console: Management - <Domain> - Options - Unknown Accounts.

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

5.2.2

Mailbox has exceeded the limit

Recipient's mailbox is full and C_Mail_SMTP_Other_FullMailboxPermanentError has been set.

Check recipient's quota on server/domain/user levels.

554

5.3.4

Message size exceeds fixed maximum message size

Too many data was sent by the user. User account has an amount limitation.

You can increase or disable amount limit from administration console - Management - <User> - Limits tab. Make sure all 3 levels (server, domain and user) are set to 0 (stands for unlimited).

554

5.7.1

Permission denied

1) Access restriction to all services is enabled and sender's IP address was found in denied list.

2) User sent some data before greeting from server was sent.

3) Milter filter returns error in connect stage.

1) Check service's access list in System - Services - <Service> - Properties - Access or disable the C_System_Services_Firewall API variable

554

5.7.1

Message cannot be accepted, rules rejection

1) Sender is blacklisted.

2) External filter rejects the message.

3) Milter filter returns error in eom stage.

1) Check system and recipient's blacklist.

2) Check used external filters.

3) Check used external filters.

554

5.7.1

Message cannot be accepted, virus found

Virus was found in the message body or in the message attachment.

If you think the attachment is not harmless (false positive), try to alter the configuration of the antivirus engine (Quarantine instead of Reject), or create a Bypass entry.

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 administration console.

554

5.7.1

Message cannot be accepted, spam filter rejection

Message is probably spam.

If you think this message is spam (false positive), try to alter the configuration of the Antispam engine, index the message by Bayesian or create a blacklist entry.

554

5.7.1

Message cannot be accepted, spam rejection

Message is probably spam.

If you think this message is not spam (false positive), try to alter the configuration of the Antispam engine, index the message by Bayesian or create a whitelist entry.

Message deleted by filter

Alter your content filters configuration.

554

5.7.1

Message cannot be accepted, filter rejection

The message was rejected.

Check your filter settings and configuration.

554

5.7.1

Permission denied. Maximal parallel connections from this IP reached

Number of connections coming from particular IP address exceeds the limit of maximal number of parallel connections.

Click the Bypass button in intrusion prevention settings (SMTP specific rules) to specify an IP address (or a range of IP addresses), where this limit is not applied.

Or increase the value of c_mail_smtp_general_parallelipconnectionslimit variable. Zero means no limit.

554

Could not connect and send the mail to recipient

Client session - target server not responding

Check target server.

554

Could not verify SSL connection

Client session - target server SSL certificate cannot be verified

Check target server.

554

Permanent problems with the remote server

Client session - server returned 4xx or 0xx status

Try again later.

554

... while issuing MX query

Client session - cannot obtain MX for target server

Check DNS

554

Could not resolve target DNS

Client session - cannot contact DNS

Check DNS

554

Too many hops

Message was redirected by more than C_Mail_SMTP_Other_MaxHopCount SMTP servers

Check mail delivery path recorded in the Received headers.