Administrator-Defined IP Allow Lists and IP Block Lists

Administrator-Defined IP Allow Lists and IP Block Lists

Administrators of Edge Transport servers maintain administrator-defined lists of IP addresses. You can enter and delete the IP addresses that you want to allow or block by using the Exchange Management Console or the Exchange Management Shell. You can add IP addresses individually, by IP address range, or by IP address and subnet mask.

When you add an IP address or IP address range, you must specify the IP address or IP address range as an IP Block address or an IP Allow address. Additionally, you can specify an expiration time for each IP Block List entry that you create. When you set the expiration time, the expiration time specifies how long the IP Block List entry is active. When the expiration time duration is reached, the IP Block List entry is disabled.

By using administrator-defined IP Allow lists and IP Block lists, you can configure connection filtering to support the following scenarios:

• To exempt IP addresses from the IP Block lists of IP Block List providers - You may have to exempt IP addresses from the IP Block lists of IP Block List providers when legitimate senders are unintentionally put on an IP Block List provider's IP Block list. For example, legitimate senders could be unintentionally put on an IP Block list when an SMTP server was unintentionally configured to act as an open relay. In this scenario, the sender will probably try to correct the misconfiguration and remove their IP address from the IP Block List provider's IP Block list.
• To deny access from IP addresses that are a source of unsolicited e-mail messages but are not found on an IP Block List provider's IP Block lists - Sometimes, you may receive a large quantity of unsolicited messages from a source that was not yet identified by a real-time block list (RBL) service to which you subscribe.