IP/Domain Warmup

New IP addresses always look suspicious to ISPs until their sender reputation elevates enough to positive. There are several factors which are considered negative when sending emails from a new IP, and consequently takes time to achieve maximum deliverability, and avoid the spam folder. 

Infobip aims to help you ensure as high email deliverability as possible using IP/domain warmup. Once your domain reputation has increased enough to a reputable standard, you will be able to send campaigns with full deliverability. 

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 Internet Services Providers (ISPs), and target engaged users at the same time. 

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

The goal during your warmup process is to send to subscribers who are least likely to complain and bounce. This would include those that have opted-in most recently and are consistent openers/clickers. 

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, anything less than weekly it will take more time to build a positive sender reputation. 

For every new domain used via the web portal, there will be 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. 

To preserve the domain reputation while full operative sending, Infobip monitors traffic and bounce rates. If the bounce rate exceeds 5% of the total traffic over the last 24 hours, the service will be temporarily blocked. This ensures your reputation remains established and doesn’t portray a high bounce rate. 

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.

Automated Warmup 

Automated IP/Domain warmup is the easiest way to properly perform a warmup and establish the highest delivery rates. Automated warmups are by default enabled for domains added to the web interface.

When you register domains and set up new email campaigns, you can refer to the Warmup field in Email settings to see how many emails are eligible to be sent that day.

If your campaign is larger than the limit shown for that day, the remaining emails will be sent out the next day, whilst still conforming to daily limitations. 

Example: You set up a campaign with 10,000 daily emails and you are using a new domain with a dedicated IP: 

• During domain setup, you will input max daily traffic per domain. That traffic will be base traffic to calculate domain warmup schedule. For this example, your max daily traffic will be 10k 
• Once set up and your emails are ready to be sent, you’ll see in the email dashboard at which stage warmup is at for the domain, along with how many emails can be sent. 
• As you are using a new domain, the first day of your permitted traffic range will be 200 emails. The remaining will be scheduled to send over the coming days according to daily limits. 
• The second batch of 400 emails being scheduled to send in 24 hours and 5 minutes. Five minutes are added to ensure that there are no crossover issues between days. 
• The third batch is, as previously sent at another +100% of the previous day (800 emails), is sent 24 hours and 5 minutes later, and so on. 
• Infobip repeats this procedure until all emails are sent. Once the max daily traffic for a domain is reached, the sender domain is classed as “warmed up” and there will be no further limits on sending. 

Here are some points to look out for when using automatic warmup: 

• During automatic warmup, only one campaign can run in parallel 
• When max daily traffic is reached, several campaigns can be run in parallel (using warmed up sender) 
• If you start using a new domain, the same procedure follows as in the example above 
• If your max daily volume increases more than 100% than first specified, the sender will re-undergo warmup until the new max daily limit is reached 

Manual Warmup (API) 

The best way to manually ensure optimal email deliverability is to follow a simple 14 day warmup plan.

	Daily Volume
Day 1	200
Day 2	500
Day 3	1000
Day4	2000
Day 5	5000
Day 6	10,000
Day 7	20,000
Day 8	40,000
Day 9	100,000
Day 10	250,000
Day 11	500,000
Day 12	1,000,000
Day 13	2,000,000
Day 14	5,000,000

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

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

If you find that you are warming more than 5,000,000 it is advised not to exceed this volume.