Why a Sending History is Important to Reaching the Inbox

Posted by John Pollard on

One of the most common problems I see with marketers today is a poor sending reputation due to not having enough sending history on an IP address. Many marketers that are starting a new email program or changing IP addresses aren’t always aware of the consequences of sending from a new IP address and trying to send to their entire subscriber list from day one. Unfortunately, this practice resembles a popular spamming technique called IP hopping and the result is that ISPs are very suspicious of new IP addresses.

To combat IP hopping spammers, ISPs monitor and track the sending history on an IP address and place restrictions on email coming from a new IP address to ensure it is being used by a legitimate sender. The restrictions involve limiting the amount of email they allow (throttling) as well as intentionally placing email directly in the junk folder to see if your subscribers will classify your message as “not spam.”

What should a marketer do to establish Sending Permanence and a good sending reputation on a new IP address?

The answer to this question is to take the new IP address through a warm-up process that works within the ISP restrictions over a period of time. An ISP wants to protect its members from spammers, so working within their rules can help your IP establish a positive sending history and a good sending reputation. Below is a list of seven simple tips to help you get started warming up your IPs:

  1. Deploy from a sound infrastructure: A correctly configured DNS, such as reverse DNS (PTR) records and authenticating with SPF and DKIM tells an ISP that you are more likely a legitimate sender.
  2. Sign up your IP address with all available feedback loops: Maintaining a low complaint rate is a primary factor in determining your sending reputation. Spammers don’t care about complaints and IP addresses with high complaint rates experience ISP blocks and email being sent to the junk folder.
  3. Ensure your bounce process is set to remove unknown users after one bounce: Maintaining a low unknown user rate is another primary factor in determining your sending reputation. IP addresses sending to a large number of unknown users experience ISP blocks and email being sent to the junk folder.
  4. Clean up your email list of inactive and unengaged subscribers: Spam traps are inactive email addresses created by an ISP to catch spammers or marketers with bad list hygiene practices. IP addresses sending to a large number of spam traps experience ISP blocks and email being sent to the junk folder.
  5. Send to your best subscribers first: Your best subscribers are those that are actively engaged with your email program (e.g. high opens, click-throughs and conversions). These subscribers give your new IP address high engagement metrics which tells an ISP that your email is legitimate.
  6. Start slowly and increase volume over time: ISPs limit the amount of email they will accept from a new IP address (throttling). Start sending a small number of emails to each ISP and let their spam filters get used to the sending behavior of your new IP address before increasing volume.
  7. Monitor your Deliverability: Monitor how the ISPs are treating your email during the warm-up process using Return Path’s Mailbox Monitor. Your Inbox Placement Rate is a good indicator of when an ISP’s spam filter adjusts and can help identify other deliverability problems.

Going through the IP warm-up process takes time, dedication, planning and preparation but is necessary to establish a good sending reputation.


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About John Pollard

John is a Senior Knowledge Strategist at Return Path. He is dedicated to building and maintaining knowledge and content assets to help marketers maximize the value of their email programs. John believes that sharing knowledge feeds the imagination, fosters collaboration and empowers people to grow and evolve. He has been in the email marketing industry since 2008 and has consulted numerous businesses and ESPs on deliverability and email optimization. Prior to joining Return Path, John worked in the finance industry with roles in business analysis and system administration.

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