Newsletters, webinars, promotional announcements, event invitations. Some users consider these spam, others not. The Greymail category exists in order to help you chose how strict our filters should be when filtering these types of messages.

This article applies to Administrator accounts - Quarantine Administrator accounts can view this information but cannot edit the parameters.

Administrators can manage greymail sensitivity for their domains under: 
My Organization → Parameters → Inbound Filtering → Filtering Policy Groups → Filtering

What is Greymail?

Greymail is a type of email that is commercial in nature and typically sent to a large number of people. This includes e-newsletters, invitations to different events and Webinars, and promotional announcements. The messages are sometimes sent abusively and considered undesirable by many users but some might want to receive these emails. Many organizations send greymail as part of their marketing strategy. User preferences will vary from organization to organization, and even within the same organization, as to who wants to receive what so these types of messages. They are a bit of a grey area for antispam solutions, hence the term Greymail.

How do we determine what is greymail?

An email is considered to be greymail if it contains one of these indicators:

  • It is coming from a known massmailer
  • It contains multiple marketing terms
  • It contains terms regarding an invitation to an event or webinar

Blocked messages that have been determined to be greymail are identified with a newspaper in the Cumulus Quarantine.

What can you do?

The standard behaviour is for us to try to differentiate between what is abusive and what isn't based on things like the reputation of the sending organization and third-party sender, the presence of a working unsubscribe mechanism, the organization’s respect of unsubscribe requests, and complaints of abuse we have received. Cumulus allows you to set your preferred sensitivity to Greymail.

Greymail sensitivity

Clients can establish preferences as to their global greymail tolerance by setting Greymail sensitivity to Strict or Permissive. This will increase or decrease the score of greymail messages, which influences how many Greymail messages are delivered to your users.

  • Setting the Greymail sensitivity to Strict will increase the score of greymail messages, decreasing how many your users receive.
  • Setting the Greymail sensitivity to Permissive will decrease the score of greymail messages, increasing how many your users receive.

Filter on your mail server

If you need to establish lower levels of tolerance to greymail for certain individuals within your organization, you can implement rules in your mail server that detect the presence of  Z_COMMERCIAL_MAIL in the x-spam-status header. You may then instruct your server to discard or redirect such emails.


Purchasing items online often automatically subscribes users to promotional messages even if they did not explicitly request it. This practice is prohibited in Canada but is often tolerated elsewhere in the world. When a situation like this occurs, the recipient may use the unsubscription mechanism provided by the mailer. If no such mechanism is provided, or an unsubscription request isn't respected (note that senders have 10 business days to process unsubscriptions) the message may be reported to our technical team as spam.

Block list entries

An administrator may decide to use a combination of allow lists and block lists to authorize or block mail from these companies for their users.