IP/Domain warmup

IP/Domain Warmup

Most mailbox providers (for example, Gmail, Yahoo, and Hotmail) analyze all traffic from new senders to ensure that the traffic is not malicious. For mailbox providers, a new sender is a sender that sends from a new IP address and/or from a domain.

New senders should start by sending a small batch of emails.

Well-performing emails build a positive reputation for the sender. Mailbox providers (ISPs) typically respond to a positive reputation by placing more emails in inboxes, rather than spam filters, and increasing the volume of emails they're willing to receive.

Poor-performing emails, such as ones targeting invalid or unengaged recipients, build up a negative reputation with the mailbox providers, resulting in fewer emails being placed in inboxes and a lower willingness to accept higher email volumes.

IP/Domain warmup process

IP/domain warming is the process of methodically adding campaign volume week-over-week to a new IP Address to establish a positive sending reputation with mailbox providers and target engaged users at the same time.

It is recommended that you start your campaign focused on your most reliable data about your subscribers, that is, your most engaged users. You can then add your older data and less engaged users to later segments of the warmup.

For every new domain used with the Infobip web interface, there is an automated IP/domain warmup.


If you are sending traffic via SMTP or HTTP API, you need to carry out a manual IP/domain warmup. See Manual Warmup (API).

Here are some pointers to ensure IP/domain warmup is done to the best of its ability and boosts deliverability:

  • Clean email databases by removing invalid emails
  • Only send emails to recipients who have signed up/opted in
  • Implement an email verification process during signup
  • Do not purchase lists on scrape sites

You can read many more useful pointers in Deliverability Recommendations.

Daily Traffic

Base Traffic is the maximum number of emails sent by a particular sending domain in a daily (24-hour) window, calculated over the last 30 days. To protect the domain's reputation, if no emails are sent in the last 30 days, the automated warm-up process restarts, and it is also highly recommended to rewarmup the domain in case of manual warm-up as well.

Targeted Daily Trafficvalue is set when you add or configure a new domain. You should set this value to be the amount of consistent traffic (emails/day) that you want to send from the domain. This value also acts as a threshold to decide when a domain is considered to be warmed up.

Sending Speed is calculated automatically in case the domain is in the automated warmup and it ensures there is a small pause between each email to provide better overall delivery.

Automated Warmup

Automated Domain Warmup is the process of increasing the sending speed (number of emails per day) of a domain to maintain the good reputation of a domain and IP address.

Every newly registered domain that is added using the Infobip web interface is, by default, set to use automated domain warmup, and sending speed restrictions are applied. This means that the domain can't send a large number of emails in a day, but if the domain sends regular traffic, then the automated domain warmup service slowly increases the sending speed of the domain so that it reaches the per-day mail target.


Automated warmups are applicable only to traffic that goes through the Infobip web interface.

Smart Warmup

To make the process of gradually ramping up volumes easier while taking email performance into account, Infobip's smart warmup automatically limits the amount of email that your Infobip web interface account can send out. Smart warmup works according to the following logic:

  • Any from-domain that sends more than 500 emails and generates a delivery rate of 98% or more follows the Fast Warmup(50% daily Base Traffic increment)
  • From-domains that send at least 500 emails and achieve a delivery rate higher than 96%, but lower than 98%, adjust down to the Moderate Warmup volume limits (40% daily Base Traffic increment)
  • From-domains that generate delivery rates of less than 96% see their volume limitations adjust to the Slow Warmup(30% daily Base Traffic increment)

Key Points for Automated Warmup

Here are some points to look out for while automated warmup is active:

  • New domains always have a Base Traffic of 0 and an initial sending speed of 500/Day
  • Only one Infobip web interface campaign from the sending domain is allowed at a time if the sending domain is on warmup
  • Warmup is not a one-time process but is a continuous process. At any point in time, a domain is considered warmed up or not based on the Base Traffic (if Base Traffic is two-thirds of the Targeted Daily Traffic, then it is warmed up)
  • Decrease in sending speed occurs in a scenario when a domain sends fewer emails on a consistent basis (in the last 30 days)

Manual Warmup (API)

For traffic sent over the SMTP or HTTP API, you need to carry out a manual IP/domain warmup. The best way to ensure optimal email deliverability is to follow a simple 14-day warmup plan.

The following table suggests the volume of traffic for each day in the plan.

 Daily Volume
Day 1500
Day 2700
Day 31000
Day 52000
Day 62800
Day 74000
Day 85600
Day 98000
Day 1011,200
Day 1116,000
Day 1223,000
Day 1333,000
Day 1450,000

* If additional warmup is needed, you can increase it further by 40% from the previous day's Base Traffic (delivered emails).

During the first 2 weeks, make sure that you target your most engaged subscribers. By week 3 and 4, target subscribers that have engaged within the last 60 days.

Do not target subscribers who have not opened or clicked emails within the last 90 days during the first 45 days of manual warmup.

If you plan to send over 10,000,000 emails monthly, contact Infobip directly to assist with a customized warmup plan and additional recommendations.

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