When you receive your shiny new IP, it may have little to no sending history, this is what we call a cold IP.

IP warming is an important step to acquire a good reputation with ISPs, the warming process is used to build a reputation with receiving servers that you intend to send your messages too, think of it as stranger politely knocking on doors of Gmail asking to enter rather than letting yourself in, the latter is not only is un-polite but may cause your messages to be flagged as suspicious by Gmail spam filter or blocked entirely, it’s all about building trust and confidence between you the sender and the ISP as a new sender.

ISPs are there to protect their recipient and will want to see that you are sending relevant, consent-based messages to permit your mailings into your recipient’s inbox.

ISP will monitor your IP to track your sending behaviour and are likely to accept your messages based on the sender following email best practices.

During the IP warming process, you should send consistent, low volume email campaigns, gradually increasing this volume per day until you have reached your full volume capacity.

It can take up to 4-6 weeks to complete the IP warming phase. This depends on your volume amount and how well your recipients are engaging with your messaging.

During the warming process, ISPs like Hotmail will set receiving limits on your IP until you have met their standards of good reputation.

First steps with IP warming

  • Ensure your IT team updates your DNS authentication records, SPF DKIM and DMARC.
  • Segment your data and use email validation tools to clean your recipient list before any sends.
  • Focus on your most active users only during IP warming phase, these would be recipients who have recently opened, clicked an email and that have opted-in to your mailings using the double opt-in
  • Be creative with your email content, create content that initiates recipient engagement.
  • If you are using a data list that has not been targeted or sometime, first send a welcome email, this will act as a reminder to your recipients that they have opted-in to prevent spam complaints.
  • Be consistent in your sending, gone weeks without any sends? you might have to restart your warming process.
  • Make sure you unsubscribe links are highly visible.
  • It’s very important to add a privacy policy to your website

Warming schedule

The IP warming schedule assists in gradually establishing a reputation with ISPs as a legitimate email sender.

Day Daily sending volume
1 500
2 1000
3 2500
4 5000
5 10000
6 20000
7 40000
8 60000
9 100000
10 150000
11 200000
12 250000
13 300000
14 400000
  Continue to double your volume until you have reached your target daily volume.


Steps to take during the IP warming process

  • Review your frequency and be consistent in your sending
  • Keep your abuse complaints low
  • Seeing threshold limits, stop sending and re-start the send later in the day or the next day.
  • Each day should start with your most actives, engaged recipients.
  • Seeing some blocks on your first send? don’t worry too much, stay the course, ensure you’ve implemented of the above, remove recipients from your marketing campaigns who are consistently not engaging., ISPs are trying to determine your legitimacy, as a sender.

What ISPs like to see

  • Consistent email frequency.
  • Steady opens and clicks from your recipients.
  • Consistent email frequency.
  • Email best practices are following, whether that is relating to content or list hygiene.
  • Emails are authenticated correctly (SPF, DKIM, DMARC)

What ISPs don’t like to see

  • If too many of recipients click the spam button, your IP reputation is likely to decrease.
  • Unforeseen volume increases.
  • Invalid email addresses and spam traps within your data list.
  • Very little engagement

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