MailEnable Standard Guide
SMTP - Delivery



First Retry

The delay before a message is retried for the first time. The default is 15 minutes.

Second Retry

The delay before a message is retried for the second time. The default is 30 minutes.

Third Retry

The delay before a message is retried for the third time. The default is 60 minutes.

Subsequent retries

The delay before a message is retried for the first time. The default is 240 minutes.

Failed Message Lifetime

This determines the amount of time a message will stay in the outbound queue before MailEnable gives up and moves the message to the Bad Mail directory. If the message has hit the maximum retry amounts, it will be moved to Bad Mail, even if the failed message lifetime has not been reached.

Delay notifications

When an email fails to be delivered, but the error is not permanent (which could happen if there was a network error, the remote server was down, or other errors), then MailEnable will send an email to the original sender to inform them that the message has been delayed. This option can either turn delay notifications off, send a message only on the first failure, or to send a message back for each send delay. There is also the option to only send delay notifications after a specified period of time from when the message send is first attempted. This will allow the SMTP service try to send the message more than once before the sender is informed that there is a delay.

Do not generate Non-delivery Receipts

When an email cannot be delivered and the error is permanent, then MailEnable will send a message to the original sender informing them of the error. Enabling this option will stop this message from being generated.

Only generate NDRs for senders who authenticate: This setting when enabled stops NDRs to be generated for non authenticated senders. Spammers can cause problems by sending emails which return a non delivery report to the sender. Most of the time the sender address is not the spammers address and therefore the NDR creates its own spam which is also known as email bounce back scatter.
Directly insert Non-Delivery Receipts into Inbound Queue This will insert NDRs into the SMTP inbound queue instead of the SMTP outbound queue, which is the default.
Send a copy of all NDRs to This will allow you to send a copy of every NDR generated to a specific SMTP address.
Limit concurrent connections This setting will limit the amount of concurrent outbound connections that can be made to the same server. This is useful to stop spammers that have managed to spam through the server and send large amounts of messages to the same server as this can consume all the available SMTP send threads and delay messages to other remote servers sitting in the outbound queue to be delayed. this can also reduce the risk of large hosting companies blacklisting your severs IP address because of bulk sends.


Delivery failure notifications can be customized for the SMTP service. Templates can be used for either a post office (if the message which fails can be attributed to a post office) or for the server. The template files for a post office need to be configured in the following folder:

Mail Enable\Config\Postoffices\[postoffice]

If this template file does not exist, then the server level one will be used, which is located at:

Mail Enable\Config\Postoffices

MailEnable provides two template files for non-delivery reports:




Non-Delivery Message that has a list of failed recipients (ie: one or more recipients were refused by the server)


Non-Delivery Message that has no failed recipients (ie: transmission errors, system errors)





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