When you add a new dedicated IP address to your account, you need to warm it up. You also need to warm up your IP if you haven't sent on it in more than 30 days. Warming up your IP allows you to gradually send more emails over your new IP to establish a good sender reputation.
IP warming is the practice of gradually increasing the volume of mail sent with a dedicated IP address according to a predetermined schedule. This gradual process helps to establish a reputation with ISPs (Internet Service Providers) as a legitimate email sender.
When an ISP observes email suddenly coming from a new or "cold" IP address, they will take notice and immediately begin evaluating the traffic coming from that IP. Since ISPs treat email volume as a key determining factor when detecting spam, it is best to begin sending a low to moderate volume, eventually working your way up to larger volumes. This gives the receiving email providers a chance to closely observe your sending habits and record how your recipients engage with your email.
A gradual warmup does not always guarantee a perfect sending reputation. It is still important to follow sending best practices.
It is much easier to establish a positive reputation as a new sender, than it is to repair an existing reputation.
Warmup types
There are two ways to warm up your IP. If your dedicated IP is relatively new, or you've never had one before, you need to warm up your IP manually. If you are adding new dedicated IPs to existing warm IPs, you can automatically warm up your IP with the help of MassMailer support team. When your IP is being warmed up, this is your hourly sending limit:
Manually warm up your IP
To manually warm up your IP, you need to gradually send more and more email over your IP address at the rate in our suggested IP Warmup Schedule.
The goal of warming up is to ramp up your sending volume to your anticipated “normal” levels.
Automated IP warmup
To set up automated IP warmup, you can contact MassMailer support team.
When automatically warming up an IP, MassMailer limits the amount of email sent through that IP per hour. Any email requests that exceed this hourly limit will overflow to any other existing warm IPs on your account. If you do not have any other warm IPs, you should warm up your IP manually.
Automated IP warmup hourly send schedule
| Warmup Age (Days) | Hourly Email Limit |
| 0 | 20 |
| 1 | 28 |
| 2 | 39 |
| 3 | 55 |
| 4 | 77 |
| 5 | 108 |
| 6 | 151 |
| 7 | 211 |
| 8 | 295 |
| 9 | 413 |
| 10 | 579 |
| 11 | 810 |
| 12 | 1,000 |
| 13 | 1,587 |
| 14 | 2,222 |
| 15 | 3,111 |
| 16 | 4,356 |
| 17 | 6,098 |
| 18 | 8,583 |
| 19 | 11,953 |
| 20 | 16,734 |
| 21 | 23,427 |
| 22 | 32,798 |
| 23 | 45,917 |
| 24 | 64,284 |
| 25 | 89,998 |
| 26 | 125,997 |
| 27 | 176,395 |
| 28 | 246,953 |
| 29 | 345,735 |
| 30 | 484,029 |
| 31 | 677,640 |
| 32 | 948,696 |
| 33 | 1,328,175 |
| 34 | 1,859,444 |
| 35 | 2,603,222 |
| 36 | 3,644,511 |
| 37 | 5,102,316 |
| 38 | 7,143,242 |
| 39 | 10,000,539 |
| 40 | 14,000,754 |
| 41 | 19,601,056 |
Why don't other ESPs require IP warmup?
Many other email service providers do not offer dedicated IP addresses to their customers - they place all of their customers on shared IP groups by default. Warming up is not required for a shared IP group - MassMailer handles this automatically.
Having a dedicated IP allows you to control your own reputation completely, and prevents your sending from being impacted by the reputations of other MassMailer users.