SYMPTOMS

Clients or remote servers sending email via SMTP to the mail server are given an error that the connecting IP address has been "denied access".

CAUSE

The IP address of the inbound connection has been denied access due to being listed in the SMTP Access Control properties of the MailEnable administration program. IP addresses can be added here both manually and automatically depending on options.

Example error:

530 example.com ESMTP MailEnable Service, Version: 9.00--9.00 denied access at 01/01/17 17:00:00

RESOLUTION

1. Navigate within the Administration console to the following location: Servers->localhost->Services and Connectors, right click on "SMTP" and select "Properties" in the popup menu.
2. Navigate to the "Inbound" tab and click on "Access Control".
3. If the Access Control option is set to "Granted access", then ensure the IP is not in the list being denied access. If the Access Control option is set to "Denied Access" then the connecting IP address needs to be listed in order to be allowed access.

MORE INFORMATION

The incoming IP address can automatically be added to the inbound "Access Control" list if the SMTP security "connection dropping" option is enabled along with the option to ban. The SMTP service will drop the connection when the failed number of commands or recipients is exceeded (during the one SMTP conversation) and add the IP address to the inbound "Access Control" list.

The SMTP Debug log will have the following line in it when it bans an IP address:

ME-I0073: IP Address 123.123.123.123 banned.

It is recommended to not enable the autobanning. It is normally better to use the abuse detection option instead. If you use autobanning do not lower the value for the failed number of commands to a low number. If an IP address has been whitelisted in the SMTP settings, it will not be autobanned.