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How To Stop Spam Email in Microsoft 365

​Spam e-mails have been around a very long time and bad actors have used them since the beginning to gain sensitive information from users​. These bad actors continue to get more intelligent in the ways they put together these spam e-mails and they can look like any normal mail that may come to your inbox. Because of this, it's important to have good processes and settings in place to help filter these types of mail out of your inbox and into your Junk, as well as to make them easily recognizable.

There are many ways that you can help block this type of mail, some of which are default settings within Microsoft 365 (M365) and others that are custom tools. First, let's see what default settings in M365 that we can put in place on a tenant to help deter spam mail:

  1. Adjust the spam filter - In M365, there is a spam filter setting where the strength can be adjusted based on how strict you would like the filtering to be. The strength settings are in number form from 0-9, with 0 being the most restrictive and 9 being the least. This can really help in restricting spam mail to the inbox.
  2. Block Address Domains - If he user is seeing an abundance of spam mail coming from a single domain/address, this can be blocked in M365 so it does not end up in their inbox. Any domain can be blocked with no limit to how many can be blocked. On the contrary to that, domains can also be whitelisted if they are ending up in the Junk folder and should be in the Inbox.
  3. Mark messages as spam based on criteria - In M365, messages can be marked as spam based on specific criteria set. For instance, mail can marked based on certain language that is used within the e-mail and/or geographic origin. 
  4. Mail transport rules - An Admin on the tenant can create specific mail transport rules that can mark messages as spam based on certain conditions that are met. For example, if spam messages are commonly received with the same subject or content in the body, specific phrases can be added to the condition to mark these messages as spam. There are many different conditions that can be set and we can customize those based on specific needs.
The M365 spam filter is pretty intelligent for being a default function, and will read headers as well as check SPF and DMARC settings to ensure the e-mail is configured correctly to deliver to the inbox. We can certainly help set all the default functions up based on the needs and patterns of spam e-mail within the tenant.

Cloud Protect Spam Filter

Other ways to block spam mail is with custom tools. RyanTech built a custom spam filter called the Cloud Protect Spam Filter (CPSF) which can add a extra layer of protection, and works in conjunction with the M365 spam filter settings you might already have in place. The Cloud Protect Spam Filter is highly intelligent and offers separate, more extensive functionality to further protect the users. Here are some more details in regards to what the Cloud Protect Spam Filter can do:

  1. Like the M365 spam filter, the CPSF will check the headers of every inbound e-mail to ensure accurate configuration is in place, but the CPSF will also read the subject and body of the e-mail to verify the language and tone of the message and can mark it as spam, or legit, based on that information. It is important to note that this information is NOT stored in the tool after review.
  2. CPSF will download any attachments within the email before delivery to ensure there are no viruses in the e-mail or attachment itself. It is very common for attachments sent through e-mail to be compromised.
  3. CPSF is 100% API based, which means it operates differently than a typical spam filter. A typical spam filter re-routes the mail through the filter and this adds an interruption within the mail flow and a potential risk of a breaking point in the flow. This will not happen with the CPSF.
  4. The CPSF can be deployed with the click of a button by the user/admin
  5. CPSF will natively mark e-mails as being 'EXTERNAL' with a badge including information about the sender. See below:


Whether it be utilizing the default functions in M365 for spam filtering or our custom Cloud Protect Spam Filter tool, RyanTech is here to help and guide you every step of the way. If you would like to learn more about any of the spam filter functions within M365, please reach out to us and we can answer all of your burning questions. If you would like to get a demo of the Cloud Protect Spam Filter, click here, and we can show you all of the security advantages it can offer.


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