Implementing a warm-up strategy for EXM Delivery Cloud accounts

Current version: 10.0

Warming is the process of methodically adding campaign volume week-over-week to your account to establish a positive sending reputation with Email/Internet Services Providers. (ESPs/ISPs).

This warm up period applies to clients on shared IP pools and dedicated IP addresses.

Warm-up summary

ISPs view emails from your domain, and from a new IP address as suspicious until they can determine a positive sending reputation. It takes 4-8 weeks to achieve maximum deliverability (depending on targeted volume and engagement). Warming may take longer if your email campaigns are not perceived as “opted-in”. Certain receivers limit senders to thresholds until they build a sender reputation.

Sitecore recommends starting with your cleanest, most engaged, email list first. Focus on warming your most engaged subscribers (defined by recent orders, visits, opens, repeated clicks and subscriptions) and then add in the older/lesser engaged segments as you progress. Older segments should be combined into your campaigns in chunks of 15% of your existing volume to prevent tipping your reputation from good to bad.

The goal during your warm-up process is to send to subscribers who are least likely to complain and bounce.

During the warm-up phase the more consistent you are with volume, frequency, complaint and bounce levels, the faster you will establish a positive sending reputation. If you send infrequently (less than once a week), it will take more time to build a positive sender reputation.

The following table displays the daily volumes you should consider when planning your warm-up. You must manually implement the warm-up plan.

Week 1

Daily volume


Day 1


  • During weeks 1 and 2 send to the most active subscribers, sub 30 days active.

  • During weeks 3 and 4 send to 60 days active subscribers.

  • Do not send to subscribers that have not opened or clicked in the past 90 days during the first 45 days of warm-up.

  • If warming above 5 Million do not send more than double the previous volume.

Day 2


Day 3


Day 4


Day 5


Day 6


Day 7


Week 2

Day 8


Day 9


Day 10


Day 11


Day 12


Day 13


Day 14


Points to note during IP warm-up

Once you begin warming up your EXM Delivery Cloud account, you can expect some delays (throttling), bulking (dividing emails into discrete ‘bulks’ that delay in arrival) and blocking (emails are not received) to occur. Below are details of what you can expect and actions to take.

  • Bulking at Yahoo, AOL, and Gmail. These issues normally subside after a few email sends with positive metrics, however, over time you should achieve full inbox delivery. It is paramount to keep sending to engaged subscribers.

  • Delays at AOL, Microsoft and Comcast. The delays (421 bounces) will retry for 72 hours and if not delivered will bounce as a 5XX with the original 421 error in the bounce record. Delays are normal, and will lessen each day as your reputation develops. As long the messages are ultimately delivering there is no concern. However, if they are timing out in large quantities you should reduce the volume sent to that ISP.

  • Blocking by ISPs may occur if the list isn’t engaged enough. The key is to segment and target email subscribers carefully, and focus on segments that engage positively. Continued sending will alleviate blocking issues.

  • It is important to monitor your metrics and adjust the plan accordingly during the warm-up period.

Why a warm-up period is important

If you warm up too quickly, your reputation will remain low over time. A more gradual warm-up will help your reputation to grow steadily as you increase volume.

Quick warm-up

Slow warm-up

  • ISPs see volume spikes

  • Unknown senders

  • Blocks, Filtering, or Rate limiting will occur

  • ISPs see the gradual build in volume

  • Good reputation develops over time

  • Blocks, filtering and rate limiting rarely occur (they only occur when engagement and complaint rate ratios are in poor standing).

Warm-up helps build your sender reputation

Sender reputation is how receivers view you and your mail.

Email reputation controls access to the inbox.

  • If the sender has a bad reputation, email will be blocked or placed in a Spam folder.

  • If the sender has a good reputation, the email will be placed in the Inbox.

Reputation can affect the domain and/or IP address. It's based on the following parameters:

  • Spam complaints

  • Invalid email addresses (hard bounces)

  • Spam trap hits

  • Authentication (e.g. DKIM)

  • Third-party blacklisting

  • Engagement

The following actions have positive effects on your reputation:

  • Opens

  • Clicks

  • Authentication

The following factors have a negative effect on your reputation:

  • Poor or insufficient permission

  • High recipient complaints (report as spam)

  • Poor list quality/hygiene – bad email addresses

  • IP address and domain blacklisting

  • Spam trap hits

  • Large spikes in volume

The fundamentals of reputation

There are a number of fundamental elements to remember with reputation.

  • It is important to value those subscribers who have Opted-In to receiving email communications.

  • If subscribers do not engage with your email, your reputation may suffer.

  • Receivers (such as Inbox providers, Google, or Microsoft) and metrics can directly impact the emails that are delivered to an inbox.

  • You cannot transfer reputation from another previously used Email Marketing provider.

  • Your reputation is based on the domain used. If you use a new IP address in the same domain, the reputation may be inherited. ISPs use the reputation of the domain coupled with the reputation of the IP, therefore you must follow the warm-up process.

  • ISPs trust metrics from their users and what they observe. So no brand will get special treatment over another.

  • B2B senders must follow the same warm-up process as B2C senders as many business domains are now hosted by Yahoo, Outlook, Gmail, AOL, etc.

Permission and engagement is key for reputation

Permission is an important factor in building a good sender reputation. Subscribers complain about mail they are not expecting to receive. To help prevent this, check the following:

  • Are you sending more frequently than you said you would?

  • Did they sign up for exactly what they are receiving?

  • Are you sending content other than what you said you would?

  • Are you following best practices by staying up to date on the Can-Spam act and the CASL legislation?

Why engagement is important

Engagement is important because ISPs track how engaged subscribers are with an email and its sender, and the nature of the engagement.

  • Positive actions may include opening a message, adding an email address to the contact list, clicking through links, clicking to enable images, and read rate such as scrolling through the message.

  • Negative actions may include reporting the email as spam, deleting it, moving it to the junk folder, or ignoring it.

  • Engagement ratings are another compelling reason to use only opt-in or confirmed opt-in email marketing lists. Opt-in maximizes the likelihood of engagement, because in theory there is a relationship already established with the receiver.

Quality always wins out over quantity

There is a charge for the volume you send. If the message is never opened that cost is wasted.

  • Your Return On Investment (ROI) will be lower if you include disengaged subscribers in your campaigns.

  • Disengaged subscribers are the common cause of complaints, spam traps, and hard bounces and these can affect the deliverability or inbox placement to engaged subscribers (which lower your ROI).

  • Run regular re-engagement campaigns to win back the disengaged subscribers.

  • Send to the disengaged subscribers less frequently than engaged subscribers.

The following strategies help to keep your list highly engaged:

  • Send relevant content to engaged subscribers.

  • Set subscribers’ expectations from the beginning.

  • Give people who opt- in to your subscription lists choices on how often they’ll receive emails from you (for example: once daily, a weekly digest, or as items become available or go on sale). If you send infrequently, make that clear. Ask them to whitelist you as they opt-in.

  • Deploy a good onboarding program educating them on expectations.

  • Begin with your registration forms. If you have the option to block spam-like, personal, or role-based email addresses, do so.

  • As your lists age, weed out non engaged subscribers.

Spam traps

Spam traps are email addresses that are used to identify spammers. They are sometimes referred to as honeypots.

Pristine spam traps are email addresses created by either a mailbox provider or a blacklist with the goal of preventing malicious mail. These email addresses were never owned by a real person, do not subscribe to email programs, and of course will never make a purchase. If you are hitting pristine traps, this typically indicates you have a bad data partner.

Recycled spam traps are email addresses that were once used by a real person but abandoned and then recycled by ISPs as spam traps. Before turning on an abandoned email address into a spam trap, ISPs will return an unknown user error code for a period of time (6 to 12 months). If you are hitting a recycled spam trap, this typically indicates that your data hygiene process is not working.

To help avoid and remove spam traps:

  • Do not purchase or rent lists.

  • Remove hard bounces.

  • Continuously re-engage your inactive subscribers.

  • Remove disengaged subscribers once several re-engagement attempts have been made.

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