What is IP Address or account Warm Up strategy?

Definition of IP warm up

IP warm up is the process of gradually sending emails over a period of time in order for email service providers to establish a positive reputation regarding the IP address used in sending.

How IP warming up works?

Initially a combination of IP address and sender domain is used to check for reputation. If it doesn’t already exists, it’s suspicious until it has a proven track history of positive interactions with those emails.

Positive interactions are considered to be opens and in some cases clicks (the higher the best) and low hardbounces or spam events.

Some email providers also have thresholds for senders. For example you can not send 100.000 to yahoo email addresses in a very short time interval (~30 minutes), as you’ll start getting errors.

The warm-up plan

Note that for new lists of subscribers, it makes sense to have a more steady warm-up plan, compared to warming up a new IP address for existing emails.

  • First 2 weeks only send to most active subscribers.
  • Week 3 and 4 expand to email subscribers who are less active.
  • Do no send to subscribers who didn’t open nor clicked in the last 6 months.
DayDaily volume
Day 1200
Day 2500
Day 31,000
Day 42,000
Day 54,000
Day 67,000
Day 712,000
Week 2 
Day 820,000
Day 930,000
Day 1040,000
Day 1150,000
Day 1260,000
Day 1370,000
Day 1480,000

Use the following formula to grow your daily rate:

Week1: Day N = Day N-3 + Day N-2 + Day N-1

Week2: Grow with 6-10k per day, depending on total list size.


What could happened?

You might be blocked by email providers if the list isn’t engaged enough. Try using segmentation carefully for higher engagement.

Do no stop sending, even though you might see delays in delivery.

If you have a high number of complaints (spam), then you might need to consider cleaning the list. Also consider GDPR if you don’t have permissions for the list.

Always do this warm-up with someone from our system. We have access to some logs for email delivery that allows us to better monitor the evolution.


Warming IP an account is not an easy job. Our recommendations to do it, in a more structured way:

  • start with transactional/workflow campaigns. Change ESP for the best converting ones (confirmation emails, cart recovery and so on)
    • increase number of campaigns that use the new ESP weekly
  • then next step is to use recurring campaigns for users who are very engaged with your business
    • increase number of campaigns that use the new ESP weekly or every 2 weeks
  • follow the estimated delivered emails for those campaigns with the table above
  • when you reach a few thousands emails per day you can start sending small newsletters (Segment most active customers) and increase this number in batches.

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