SpamTitan

ESMTP Settings

SpamTitan supports several extended SMTP (ESMTP) functions. These include the ability to pipeline commands, set the server to check message size before accepting transfer, create delivery status notifications in MIME format, and provide message de-queuing.

Go to System Setup > Mail Relay > ESMTP Settings to view ESMTP settings.

Important

All ESMTP functions are enabled by default. It is recommended that they stay enabled unless disabling them is necessary for your particular system setup.

The table below describes the different ESMTP settings.

Setting

Description

DSN extension:

If enabled, SpamTitan Gateway supports incoming requests to return delivery status notifications to the sender for failed, delayed, delivered and relayed messages.

If disabled, SpamTitan Gateway does not return delivery status notifications for SMTP messages.

ETRN extension:

If enabled, SpamTitan Gateway accepts inbound pull requests from other SMTP hosts to transfer messages destined for the calling server.

If disabled, SpamTitan does not accept inbound pull requests from other SMTP hosts.

ETRN Access Restrictions:

The ETRN Access Restrictions provides a mechanism to specify which clients may request the ETRN extension. The options available are:

  • Allow all: Any SMTP client may issue an ETRN request.

  • Allow only specified: The Access list table lists IP addresses and networks that may request the ETRN service. All other hosts will not be permitted to use the service.

  • Allow all except specified: The Access list table lists IP addresses and networks that are blocked from using the ETRN service. All other hosts will not be allowed to use the service.

SIZE extension:

If enabled, SpamTitan Gateway declares its maximum message size to connecting hosts and checks the sending host's estimates of message size before accepting transfer. If the sender indicates that a message to be transferred is larger than the maximum size, SpamTitan Gateway returns an error indicating that it will not accept the message.

If disabled, SpamTitan Gateway does not advertise its maximum message size or check inbound message size before transfer.

Pipelining extension:

If enabled, performance is improved as SpamTitan Gateway is allowed to accept multiple SMTP commands in the same network packet.

If disabled, SpamTitan Gateway does not accept multiple SMTP commands in a single packet.

Important

While disabling this setting helps prevent spam, legitimate email may also be rejected.

8-bit MIME extension:

If enabled, SpamTitan Gateway accepts 8-bit messages, allowing reception of unencoded multibyte characters.

If disabled, SpamTitan Gateway requires inbound messages containing 8-bit characters to be sent using 7-bit ASCII encoding.