SYMPTOMS

When sending to remote servers the following example bounce message can be returned to the MailEnable sender. The following is just an example of many ME-E0193 bounce messages.

MailEnable: Message Delivery Failure.

Reason: ME-E0193: [(MailEnable_messageID).MAI] Message Delivery Failure.

Your message addressed to the target domain (example.com) could not be delivered because the mail server responsible for this domain returned a permanent error.

The server returned:

554-mail.example.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.

CAUSE

The ME-E0193 error is indicating that the remote server has disconnected on the first connection attempt and returned a permanant failure.

The following are some basic reasons that can contribute to the error:

1. No valid Reverse DNS record (PTR).
2. Your server has been detected as a source of spam
3. Your server is open relay and has been blacklisted

There are many more reasons why the error can occur, most of the times the remote server will include a URL link within the SMTP transaction and will be displayed within the bounce message. Navigate to the URL within the bounce message for further information in regards to the rejection.

RESOLUTION

1. No Reverse DNS record (PTR):

The following links can assist in determining if a valid PTR record is returned:

• www.mailenable.com/tools
• www.dnsstuff.com
• www.dnsgoodies.com

More information on how to obtain a valid PTR record can be found within the following knowledgebase articles:

http://www.mailenable.com/kb/content/article.asp?ID=ME020206

http://www.mailenable.com/kb/content/article.asp?ID=ME020115

1. Your server has been detected as a source of spam:

A common cause of IP blacklisting is the redirection of spam messages. This can occur if mailboxes receive large amounts of spam which are then redirected to remote addresses hosted on remote servers. The most common scenario is when catch-all accounts have been enabled within a postoffice and have been configured to redirect off to large hosting servers such as Yahoo, Hotmail and Gmail. It is recommended not to configure redirections to external addresses within catch-all mailboxes.

If mailboxes are receiving spam messages then it is best to determine where the spam is originating from and implement the relevant security and filtering options. The following knowledgebase article can assist:

http://www.mailenable.com/kb/content/article.asp?ID=ME020391

One workaround if redirections are to be used on mailboxes is to configure the postoffice connector redirection properties to redirect the received message as an attachment. This will help bypass any message content filters that have been enabled on the remote servers and may help stop your server being blacklisted and considered as a source of spam.

The postoffice redirection properties can be found within the following location within the administration console:  Servers>localhost>connectors>postoffice:

• Right click on "postoffice" and select "properties" in the menu.
• Within the "General" tab navigate to the "Redirection handling" section.
• Use the dropdown menu for "Redirection handling" and set the option to "Redirect as an attachment".

1. Your server is open relay as has been blacklisted:

When configuring relay settings in the SMTP connector always ensure you have "Allow relay for local senders" disabled as this will eliminate any unwanted mail sender to relay without using authentication credentials. This is called a "Open server relay".

The recommended relay settings within the MailEnable SMTP>Relay properties is to ensure that the option "Allow relay for authenticated senders" is enabled.

More information regarding relay settings can be found in the following knowledgebase article:

http://www.mailenable.com/kb/content/article.asp?ID=ME020001

Information on how to determine if a spammer is relaying through your server can be found here:

http://www.mailenable.com/kb/content/article.asp?ID=ME020280

Information on how MailEnable determines who can relay can be found in this knowledgebase article:

http://www.mailenable.com/kb/content/article.asp?ID=ME020034