Spam Frequently Asked Questions


This article covers all of the main features of the inbuilt MailEnable spam protection. The document also answers some questions that MailEnable support often receive in regards to spam protection.


What is SMTP Domain Blacklisting?

Refer to:

Blacklisting methods:  Article ME020084

How do I configure Reverse DNS Blacklisting?

Refer to:

How to configure Reverse DNS Blacklisting: Article ME020162 

How can I create and manage my own Reverse DNS Blacklist Server?: Article ME020271

How can I block IP addresses using SMTP access control lists?

Refer to:

Blacklisting methods:  Article ME020084

How can I stop inbound email from senders that are not registered mail servers?

MailEnable provides the ability to check for a PTR DNS record for inbound connections. This can be useful to block email from cable/ADSL connections, which is where a lot of spam originates. This option is defined under the Security properties of the SMTP connector as Require a PTR record for unauthenticated connections.

How can I stop messages that come from invalid domains?

You can stop messages from invalid domains by enabling the Reject mail if sender address is from an invalid domain option in SMTP security properties. This setting will validate the existence of a mail/return path DNS records for the domain name of the message sender address. This also helps validate that authenticity of the sender address.

Why do unwanted messages keep getting delivered to a specific mailbox

If you keep receiving unwanted messages in a specific mailbox, then check if there is any catch-alls enabled for any domains configured in the post office. The reason is that spammers make up fake email addresses for that domain, so if there a catch-all configured all the messages sent from the spammer will go to the catch-all account. There is also an option in the SMTP>Security properties to disable the catch-all option. Another possibility here is if the configured catch-all account has a redirection configured to redirect to another mailbox.

What is SPF (Sender Policy Framework)? And how can it protect my server from spammers?

Information on SPF settings and configuration can be found here: Article ME020345

Can I use Third-party spam software with MailEnable for spam protection

Yes. Some third-party spam utilities are listed here: Article ME020344

What is Bayesian Filtering?

Information regarding Bayesian filtering can be found here: Article ME020346

How do I implement spam/message filtering in MailEnable?

Refer to: Article ME020189

How do I mark messages as spam and have them delivered to a Junk-Email folder?

Create a message filter to meet specific criteria and have the filter action to Mark messages as spam. You can then enable a setting under the Post Office > Properties window which will deliver any messages to Junk-Email folder if the message has been marked as spam. You can find this setting in the post office properties window under the feature selection tab.

Filtering Options

Greylisting (Professional and Enterprise versions)

This feature can be found in the SMTP properties->Greylisting window of the MailEnable administration program. Greylisting will change the SMTP service to not accept any message on the first send by the remote server and instead will send back a temporary error (an SMTP error code 4xx). The temporary error will indicate to the sending server to retry. Spammers generally do not retry sending an email, and treat the temporary error as permanent, which effectively stops the spam.

There will be a delay in inbound message delivery where the sender does not authenticate, or has not recently sent to the server. The delay time varies depending on the retry intervals for the sender server, but in most cases will be within 10 minutes. Whitelisted IP addresses bypass greylisting.

Outbound Whitelisting

Outbound whitelisting is configured in the SMTP properties->Whitelisting window of the MailEnable administration program. When enabled, the SMTP service will whitelist any IP address it sends email to, assuming that you don't want to block email from IP addresses you send email to.

Spam Protection

Spam protection within MailEnable is a weighted filtering system that accumulates points for each factor of a message that could be considered spam.  The spam protection values can be found in the spam protection under the Messaging Manager in your MailEnable Administration Program. The goal here is to find a perfect balance of points per message for your spam.   Each one of the values would not necessarily be deem a message as spam on its own but if several fail then the chance of the message being scored being spam is considerably higher.

PLEASE NOTE - The spam protection filter will do nothing to the message except add a header line to the message. This header is then checked when a message is being delivered to a mailbox, and an action may be performed, depending on what the user has configured under their Spam Protection options in webmail. One of the following values depending on the score of points compared to the threshold you set in the spam protection values will be added:

X-ME-Spam: Low

X-ME-Spam: Medium

X-ME-Spam: High

Here is an article that helps with testing this service and explains more about its usage:

Article ME020493

Webmail Report As Spam Option (Enterprise Only)

If you right click on a message in the web mail message list you will see an option to "Mark As Spam" the action of this selection is managed in the following location in Enterprise only; WebMail Properties->Spam->Report as spam menu option This is a way to collect more spam messages for your Bayesian dictionary.  Or the other effective method for larger servers can be the report as spam function which will mark an IP as a bad sender for a set period of time if the IP is reported a configured amount of time. These settings mentioned here can be found in the following location; SMTP Properties->IP Blocking->Refuse email from IP addresses.


How to reduce incoming spam: Article ME020008

Spam protection feature availability in MailEnable:

Product:MailEnable (Pro-Any Pro-1.X Ent-Any Ent-1.X)
Keywords:spam anti-spam anti spam filters filtering bayesian, SPF, sender policy
Class:FAQ: Frequently Asked Questions
Revised:Sunday, May 15, 2016