IP Warmup

When you send emails from a particular IP, you’re contributing to its email reputation. Positive stats coming out of the emails you send (high open rate, lots of clicks, etc.) boost the reputation. Whereas, negative ones (high bounce rate, many spam reports, etc) drag it down.

Email reputation is extremely important because it’s a major contributor to one’s deliverability. If you want to deliver your emails, you should be sending them from a reputable IP.

Mailtrap offers both a pool of shared IP addresses as well as an option to get a dedicated one.

Shared IP vs Dedicated IP

A shared IP is a default option with nearly all sending providers (including Mailtrap). A provider maintains a pool of IPs that are shared among their users. At any one point, hundreds or thousands of users could be sending emails from one IP and, through that, contributing to its reputation.

Sending via a shared IP is certainly cheaper. What’s more, you don’t need to build the reputation of an IP - it’s already done by the many other users and by Mailtrap itself.

Controlling the reputation isn’t easy in itself and a single, poorly executed batch of emails can wreck many previous efforts. Thus, for most senders, being on a trusted, well-monitored shared IP pool is the best solution.

An alternative approach is a dedicated IP. It’s the IP address that only you use for sending emails. As such, you have full control over your reputation and can influence it with each email sent - positively but also negatively. 

We recommend dedicated IPs only if your volume regularly exceeds 100,000 emails per month. In fact, the more you send, the better as you’ll more quickly build a solid reputation. 

If you send less than 100,000, the reputation buildup will take a lot of time and your stats may suffer during the process. So you’re probably better off sticking to a shared IP for the time being.

If you choose to use a dedicated IP in Mailtrap, you get a fresh IP that has never been used for sending emails. Before it’s at its full capacity, it’s an absolute must to warm it up.

Why warm-up an IP?

The warm-up process is basically about teaching email servers that your emails are to be trusted.

The algorithms empowering mailbox providers are very sensitive to one specific pattern. A new account surfaces and suddenly, out of nowhere, sends a batch of thousands of emails. Very often these are spam or phishing emails that should never be delivered to the inboxes.

And they’re not. In most cases, mailbox providers will block such attempts and discard these emails in no time.

If you start using a dedicated IP and follow a similar pattern, your stats will likely suffer. What’s more, many bounces or rejections will hurt your reputation straight away, making it harder to deliver any further emails too.

To avoid such unpleasant surprises, an IP warm-up process has been created. It relies on gradually increasing the volume of emails sent from a new IP while closely monitoring the stats. 

On the first day, you send out just a few hundred emails from this IP. You send a bit more on Day 2 and add some more on Day 3. Then, you may add a few hundred on day 4 and slowly add more and more until you reach the desired volume.

This way, you teach mailbox providers that you’re a reliable sender. In a few weeks' time, when you get to the desired volume and send a big batch of emails, it won’t come as a surprise to anyone.

Automated IP warmup at Mailtrap

There are many services for warming up emails and, in theory, you could do it manually too. But because it’s such a vital element of email deliverability, we built an automated IP warmup into Mailtrap. 

Each newly purchased dedicated IP goes through a mandatory 3-weeks-long (in most cases) warm-up process, aimed at giving you the best possible preparation for sending mass emails. 

Mailtrap automatically increases your volume each day, with about 30% more emails sent every day. Simultaneously, our deliverability experts closely monitor your stats. If we, for example, see that we’re moving too fast, we’ll make the necessary adjustments to the schedule.

At the moment the IP warm-up schedule looks as follows:

Day Emails sent per day Max emails per hour
1 300 60
2 390 80
3 510 100
4 660 130
5 860 170
6 1,100 220
7 1,400 290
8 1,900 380
9 2,400 490
10 3,200 640
11 4,100 830
12 5,400 1,100
13 7,000 1,400
14 9,100 1,800
15 11,800 2,400
16 15,400 3,100
17 20,000 4,000
18 26,000 5,200
19 33,700 6,700
20 43,900 8,800
21 57,000 11,400

This schedule shouldn’t, of course, limit your email sending capability. Any emails over a limit will automatically be sent via one of Mailtrap’s Shared IPs. 

For example, if you were to send 500 emails per day, the first few days would look as follows:

  • Day 1 - 300 sent from dedicated IP, 200 from shared
  • Day 2 - 390 sent from dedicated IP, 110 from shared
  • Day 3 - 500 emails sent from dedicated IP, no use for a shared IP

If your volume on any particular day is lower than what’s shown in the table above, only that many emails will be sent. 

The total number of emails sent during the warm-up process adds up to about 1.7 million. If you don’t send anywhere near that volume, the process will wrap up for you a few days earlier.

The table above also shows the hourly limit. For better deliverability, it’s always worth spreading out the large batches of emails over the course of a day, or even a few days. Mailtrap will do that for you, sending your emails throughout the day, at regular intervals.

Once the IP warm-up is finished, you’re ready to send all your emails with the freshly warmed-up IP. Good luck!

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