Page 64 - Mercury Manual.book

59 The MercuryS SMTP Server Module
General settings

The MercuryS SMTP Server Module

MercuryS is the protocol module responsible for accepting mail from the outside world using
the Internet SMTP protocol. If the MercuryS protocol module is installed on your system, you
can configure its operation by selecting it from the Configuration menu. As the primary gate-
way into your system from the outside world, MercuryS is probably the most important pro-
tocol module in the Mercury/32 suite, and it is also the most richly-configurable. Careful
attention to the settings used by MercuryS can have a significant impact on the effectiveness
of your mail server as a whole.

In the descriptions that follow, the word in brackets after the name of the configuration option
is the keyword in the [MercuryS] section of MERCURY.INI that is equivalent to that option.
When you select the MercuryS configuration option, a dialog will open, containing four pag-
es.

General settings

Announce myself as (helo) In some situations, you may wish to have your SMTP server to
tell clients connecting to it that its name is something other than the value in the Core mod-
ule’s This server’s Internet Name field. An example of a situation when this might be neces-
sary is when the core module name represents an entire domain for which Mercury is acting,
but you want it to identify itself to connecting clients using its real Internet machine name. In
the majority of cases this field can and should be left blank.

TCP/IP Timeout (timeout) the length of time in seconds that MercuryS should wait for data
on a connection before assuming that the connection is no longer valid and aborting it.

ESMTP maximum size (size) If non-zero, the maximum size message MercuryS should ac-
cept from compliant ESMTP clients. MercuryS will advertise this via the ESMTP SIZE key-
word. Not all clients, even ESMTP clients, will honour this setting.

Listen on TCP/IP port Enter here the TCP/IP port on which MercuryS should listen for in-
coming connections. The usual and default value for this field is 25, but you may want to
change this on certain occasions.

Alternate port If you wish, you can enter a second port number here, and MercuryS will also
listen for SMTP connections on that port. This can be useful to allow your travelling users to
bypass port 25 blocking restrictions implemented by many ISPs these days. The most com-
monly-used alternate port is 587 (also known as the Message Submission Port).

IP Interface to use If your computer supports multiple IP interfaces, you can use this field
to tell MercuryS which interface it should select when listening for connections: enter the in-
terface as a dotted IP address in the general form www.xxx.yyy.zzz. As an example, your
system may have one IP address assigned to a dialup PPP connection, and another, different
IP address assigned to a local Ethernet network - you would enter here the interface you need
MercuryS to use. If you leave this field blank, MercuryS will listen on all available interfaces.
Unless you are very sure of what you are doing, or have been instructed by an ISP or network
administrator, you should leave this field blank. If you change the IP interface in this field,
you must restart Mercury before the new interface number will be used.

Sender Kill File MercuryS allows you to create a file of addresses from which you will
refuse to accept mail. The file can restrict individual addresses, or (using wildcard characters)