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Email Connection Filter Settings in Office 365

18 Jul 2013 by Emma Robinson

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Connection Filtering enables you to black list or white list email messages originating from individual IP addresses or entire ranges and Office 365 now allows you to manage these options in the Office 365 Administration console.
This article is the third and final in our series of articles about Office 365 Mail Protection settings. We encourage you to also read our article on Office 365 Anti Spam settings and Office 365 Anti Virus settings for a complete picture of the mail protection provided by Office 365.
Allowed IP Addresses: Mail Originating from IP addresses in the White List do not pass through the Exchange Online Protection filters and are therefore never blocked as SPAM. Banned IP Addresses: Mail originating from a banned IP address will be immediately dropped.
You can get a detailed report of how many email messages are blocked by Exchange Online Protection due to IP this IP blocking within your Office 365 environment by signing up to our Office 365 reporting application.
To configure the Connection Filtering, you need to open up the Exchange Admin Center.

Exchange Admin Center

Exchange Admin Center


If you are using a Small Business Office 365 subscription, you can access the Exchange Admin Center using this workaround.
Click the Protection option in the left hand Navigation window and then the Connection Filter option at the top.
Connection Filter

Connection Filter


Double click the Default connection filter to make modifications.
Connection Filter Settings

Connection Filter Settings


The options themselves are quite self explanatory. Add the white listed IP addresses into the Allowed IP Address section and the black listed IPs into the Blocked IP Address section.
Note: IP addresses must be entered in the usual IP address format of nnn.nnn.nnn.nnn where nnn is a number from 0 to 255. You can also specify CIDR ranges in the format nnn.nnn.nnn.nnn/rr where rr is a number from 1 to 32. Specify ranges outside of the 24 to 32 range is obviously not recommended as it will block a LOT of email.
It is also worth mentioning that Office 365 doesn’t really support IPv6 addresses at this time.

The Enable Safe List Option

You will notice an option that says Enable safe list. Microsoft has this to say about the option:

Microsoft subscribes to various third-party sources of trusted senders. Selecting this option skips spam filtering on messages sent from these senders, ensuring that they are never mistakenly marked as spam.

We can’t find any information about who these “Trusted Senders” are or who creates this list so we can’t really comment on what it does.
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