Technical details on how Anti-spam filters work

MX Records

Anti-spam filtering is enabled by changing the domain's MX records to route incoming emails to the filtering servers first before passing the message off to the MX machines for delivery. Domains using non-DreamHost nameservers will need to manually update their MX records to reflect the change.

The filter records are:

  • MX 0 vade-in1.mail.dreamhost.com
  • MX 0 vade-in2.mail.dreamhost.com

Special considerations for forwarding addresses

There are certain things to remember with filtering in relation to forwarding email addresses. The details for the four combinations with this setup are outlined below:

  • If the domain is being filtered, and the address is being forwarded to another DreamHost email address that is also filtered, email gets sorted based on the filter mail settings of the receiving mailbox address.
  • If the domain is being filtered, and the address is being forwarded to another DreamHost email address that is not filtered, then email will not be filtered.
  • If the domain is being filtered, and the address is being forwarded to an outside address only (like @gmail), then the settings for the forwarding address' domain will be used.
  • If the domain is not being filtered and it forwards to a DreamHost email address that is on a filtered domain, the mail will get filtered.

The following table shows how Anti-spam filtering works for/with forward-only addresses. A@example.com is forward-only and sends emails to B@example.net which is a fully hosted mail account:

A@example.com uses filtering B@example.net uses filtering Is filtering done on incoming mail? What filter is used?
Yes Yes Yes B@example.net
Yes No Yes, but spam emails above score threshold are rejected. Those delivered have scoring headers appended. N/A
No Yes Yes B@example.net
No No No filtering done N/A

Headers related to filtering

All emails that pass through the filtering servers have some extra headers added.

Let's take another look at the following example:

X-vr-status  SPAM
X-vr-score  500
X-vr-spamcause  
gggruggvucftvghtrhhoucdtuddrfeekledrvdeigdduudejucetufdoteggodetrfdotffvucfrrhhofhhil
hgvmecuggftfghnshhusghstghrihgsvgenuceurghilhhouhhtmecufedttdenucgohfhorhgsihguuggvnh
ffohhmrghinhculdehtddtmdenucfjughrpeffkffuhffvtgesthdtredttddtjeenucfhrhhomhepffhrvgg
rmhfjohhsthcujfhoshhtihhnghcuoegurhgvrghmhhhoshhtthgvshhtsehgmhgrihhlrdgtohhmqeenucff
ohhmrghinhepqhhqlhgvthdrtghnpdgrhigujhgtmhgsrdgtohhmpdhonhgvlhhikhgvhihouhdrnhgvthenu
cfkphepvddtledrkeehrddvudefrdeiieenucfrrghrrghmpehmohguvgepshhmthhppdhhvghlohepmhgrih
hlqdhvkhdtqdhfieeirdhgohhoghhlvgdrtghomhdpihhnvghtpedvtdelrdekhedrvddufedrieeipdhmrgh
ilhhfrhhomhepughrvggrmhhhohhsthhtvghsthesghhmrghilhdrtghomhdprhgtphhtthhopehtrghksehi
nhhithhirghlugdruhhs

Below are details on what each field in the filter details above means:

X-vr-status

X-vr-status

This field could show any of the following:

Whitelisted
the user says always allow this email sender.
SPAM
indicates that the mail is SPAM and should be filtered into SPAM folder.
DCE
bad reputation marketing/Commercial Email should be filtered into SPAM folder.
PCE
professional marketing/Commercial emails filtered into Promotions.
MCE
miscellaneous/Small marketing/Commercial emails filtered into Promotions folder.
SN
social emails filtered into Social folder.
OK
everything is good.

X-vr-score

X-vr-score  500
The score is a arbitrary number given by Vade. It is NOT an indicator that an email is SPAM or SN or any of the other statuses mentioned. It is only used in conjunction with the SPAM status to decide when an email should be rejected because it's considered as a scam or spear phishing.

X-vr-spamcause

X-vr-spamcause  gggruggvucftvghtrhhoucdtuddrfeekledrvdeigdduudejucetufdoteggodetrfdotffvucfrrhhofhh
….
Thesghhmrghilhdrtghomhdprhgtphhtthhopehtrghksehinhhithhirghlugdruh
This is a hash of the spam cause only used by Vade.

Filtering and what it does

There are two services currently set up to filter spam. Below is a description of each:

Vade Secure
This is the filter service that scans the incoming messages for spam and other categories such as social or promotional emails. Depending on multiple factors, the message will be tagged with a status (SPAM, SN, etc) to determine if the message should be delivered to the recipients inbox, or filtered into the Spam, Social or Promotions folder.  However, spam emails that are beyond a certain threshold will be rejected.
Procmail
This is the delivery agent for the mailbox which actually places the email into Spam, Social or Promotions folders when it detects the Vade Secure headers. This is also responsible for the user defined filters defined in the panel.

Disabling filtering

Junk_Filtering_Options.png

If you uncheck 'Filter spam messages', your email will no longer be filtered into the /Spam folder. However, this does NOT disable Vade filtering. It just prevents the email from going to /Spam. It will be sent to the inbox instead.

See also

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Article last updated .