Mailbox providers evaluate the reputations of our system's individual IP addresses when they determine whether to place a message in a recipient's inbox or junk folder. An IP address' reputation is the result of factors such as how frequently it sends messages and whether content engages recipients.

To help support positive sender reputations, our system enables customers to share IP addresses. When multiple customers use an IP address, they leverage the benefit of increased sending volume.

The system also dynamically shifts senders between IPs as necessary to:

• Optimize delivery
• Prevent mailing practices of individual organizations from adversely impacting an IP's reputation for others
• Help maintain email volume through each IP

To protect overall deliverability, we use a robust set of metrics — based on your historical data and information we receive from our partner eDataSource — to grade your organization and determine which IP addresses to send your mailings from. The metrics include multiple factors including (but not limited to) how many:

• SPAM complaints we received about your messages over the past 30 days
• SPAM traps you sent messages to
• Hard bounce and block listed email addresses you attempted to send messages to

When you manage the quality of your recipient lists and follow other deliverability recommendations, you're more likely to receive a higher grade. A higher grade allows the system to assign you to IP addresses with higher reputations.

Our email specialists closely monitor email practices and, if necessary, can intervene to disable service for a sender if they violate the Acceptable Use Policy and disrupt delivery for others.