Overview of IP warm-up strategy
All information provided is taken from public sources, is for informational purposes only and does not call for action!
Definition of IP warm-up
IP address warming is the process of gradually methodically increasing the volume of email to a new IP address over a period of days to weeks in order to create a positive sender reputation with mailbox providers.
Brief description of the IP warm-up
Mailbox providers treat email from a new IP address as suspicious until they establish a positive reputation for the sender. It takes 4-8 weeks (depending on target volume and engagement) to maximize deliverability. Warm-up can take longer if mailbox providers don't realize that the email is "required" by the recipient (i.e., the recipient has explicitly signed up). Some mailbox providers limit senders to thresholds - the number of messages delivered per day - until they establish a reputation.
SparkPost recommends starting with the most effective messages - to the most interested recipients. Focus on attracting the most interested subscribers, and then add older segments as you go. Older segments should be added to engaged segments in installments of 15% of your existing volume so as not to change your reputation from good to bad. The goal in the warm-up process is to send messages to subscribers who are least likely to complain and opt-out. This can include those who signed up very recently and are constantly opening / clicking.
In the warm-up phase, the more consistent you are with volume, frequency, complaint and bounce rates, the faster you will build a positive sender reputation. If you send infrequently - less than once a week - it will take longer to build a positive sender reputation.
How many IP addresses do I need?
This is a very common question, but there is no one-size-fits-all answer. Here are some questions to ask yourself to help determine how many IP addresses are needed to support your dispatch program.
1. How many unique message threads do I have?
- Separating your message threads into separate IP addresses is a best practice and ensures that the activity of sending your marketing emails does not impact your ability to deliver transactional emails to your inbox, for example.
- Other examples of message flow: transactional, marketing, individual brands, regions, etc.
2. What is the maximum volume I need to send in one day for each message stream?
- Technically, a single IP address can send a large volume of mail quickly depending on the reputation of the sender - that's millions of messages per hour. For most senders, the recommended volume after proper warm up is between 2 and 5 million per day from a single IP address.
- Senders with less than 500k messages per month or with erratic volume from week to week may not have enough volume to build and maintain a positive sender reputation with mailbox providers. In this case, a shared pool of IP addresses can lead to improved deliverability.
IP warm-up plan
The key to success
- Within 1-2 weeks, send messages to your most active subscribers - those who have opened / clicked in the last 30 days
- Within 3-4 weeks, expand to subscribers who have opened/clicked in the last 60 days
- For the first 6 weeks, do NOT send messages to subscribers who have not opened or clicked on links in the last 90 days
- If the number of subscribers exceeds 10 million, consider adding another IP address
What to expect
Once you start warming up your IP addresses, you can expect some volume and blocking to increase. It's important to stick to the plan. The following details what you can expect and the actions you need to take.
- Increased volume in Yahoo, AOL, Gmail. Things usually clear up after a few sends with sustained positive metrics, but it may take time for mailings to be delivered. The key is to keep mailing to interested subscribers.
- Delays at AOL, Microsoft, and Comcast. Delays (421 failures) will recur for 72 hours and, if not met, will recur as 5XX with an initial 421 error in the failure record. The delays are normal and will decrease each day as the reputation develops. As long as they eventually deliver results, there is nothing to worry about. However, if the latency expires in large numbers, you should opt out of sending data to that mailbox provider by tightening the interaction window.
- Possible blocking by mailbox providers can occur if the list is not active enough. The key is to segment carefully and tighten the interaction Again, the key is to keep sending.
- It's important to track your metrics and adjust your plan accordingly during the warm-up period.
Why is the IP warm-up important?
Warming up matters
- Mailbox providers see gradual volume growth
- Good reputation develops over time
- Blocking / filtering / rate limiting is rare (only happens when engagement and complaint rates are low).
IP address warming helps build your sender's reputation
Sender reputation is how mailbox providers view you and your mail.
1. Email reputation controls access to your inbox
2. Reputation can affect domain and/or IP address and will be based on:
- Spam complaints
- Invalid email addresses (hard returns)
- Spam trap hits
- Authentication (SPF, DKIM, DMARC)
- Third-party blacklisting
- Involvement
Positive effects on your reputation include:
3. Authentication - DKIM, SPF, DMARC
Negative effects on your reputation include:
1. Poor or insufficient resolution
2. Poor list quality / hygiene - incorrect email addresses
3. blacklists of IP addresses and domains
4. Getting caught in spam traps
The basics of reputation
- Subscriptions are the most important
- If people don't want your mail, your reputation suffers
- Mailbox providers and metrics are judge and jury when it comes to delivering to your inbox.
- You can't transfer your reputation from your previously used IP.
- If you use the same domain, that reputation can follow you, but mailbox providers such as Gmail use domain reputation in conjunction with IP reputation, so you must follow the setup process.
- Mailbox providers trust their users' metrics and what they observe, so no one brand will be given special treatment.
- B2B senders should follow the same warm up process as B2C senders as many business domains are now hosted on Yahoo, Outlook, Gmail, AOL, etc.
Permission and engagement are key
Permission is the cornerstone of building a good sender reputation
1. Subscribers complain about mail they don't expect to receive.
- Are you sending messages more often than you promised?
- Are they subscribing to exactly what they are receiving?
- Are you sending content other than what you said you would?
2. Are you following best practices by complying with the Can Spam Protection Act and CASL laws?
Why is interaction important?
Mailbox providers track how interested subscribers are in an email and its sender, as well as the nature of the interaction.
- Positive actions may include opening the message, adding the email address to a contact list, clicking on links, including images, and reading speed, such as scrolling through the message.
- Negative actions may include reporting the email as spam, deleting it, moving it to a junk folder, or ignoring it.
- Engagement ratings are another good reason to only use email lists that are opt-in or verified. Signing up maximizes the likelihood of engagement because, in theory, a relationship with the mailbox provider has already been established.
Remember, quality always beats quantity.
- There is a charge for the volume sent. If the message is never opened, that cost is wasted.
- Reduce ROI by including disengaged subscribers in your campaigns.
- Disengaged subscribers are a frequent cause of complaints, spam traps, hard bounce rates that can affect the quality of inbox delivery / placement among engaged subscribers, reducing your ROI.
- Run regular re-engagement campaigns to bring back disengaged subscribers.
- Send messages to disengaged subscribers less frequently than connected subscribers.
How to maintain a high level of engagement with your list
- Send relevant content to interested subscribers.
- Set subscriber expectations from the beginning.
- Tell people who subscribe to your newsletter how often they will receive emails from you (e.g., once a day, weekly review, as products go on sale). If you send emails infrequently, clearly indicate this. Ask them to whitelist you when you sign up.
- Implement a good onboarding program that informs them of expectations.
- Keep your lists clean.
- Start with registration forms. If you have the option to block spam, personal or role-based email addresses, do so.
- As your lists age, weed out unengaged subscribers.
Spam traps
Untouched spam traps
- Email addresses created solely for the purpose of catching spammers (sometimes referred to as "Honeypots"). These email addresses have never belonged to a real person, they are not subscribed to email programs, and of course will never make a purchase. If you encounter untouched traps, it usually indicates that you have a bad data partner and/or poor list collection practices.
Redesigned spam traps
- Email addresses that were once used by a real person but were abandoned and then recycled by mailbox providers as spam traps. Before turning an abandoned email address into a spam trap, mailbox providers will return an unknown user error code for a certain period of time (6 to 12 months). If you are caught in a secondary spam trap, this is usually an indication that your data cleansing process is not working.