Bulk Email Server Guide: Warm Up

Whether you are new to the email game or are an accomplished vet, you have probably run across the idea of warming up an IP address to improve delivery performance. Warming up your IP allows you to gradually establish a good sender reputation, and is a critical step for new users or users who are adding a new dedicated IP address to their account.

What does it mean to “warm up” an IP address?

IP warming is the practice of gradually increasing the volume of mail sent via 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.

Please note that a gradual ramping warm up does not always guarantee a perfect sending reputation. It is still important to follow sending best practices. Remember to always:

  • Send content that your users want, and have explicitly opted-in to receive
  • Practice proper contact list hygiene by removing unengaged users
  • Send email at a consistent and appropriate frequency

If you are sending email from a new IP address, ISPs have no means of determining your sender reputation. Since this reputation determines whether or not your emails are delivered to your recipients’ inboxes, it is vital to immediately begin establishing a good reputation.

Remember that it is much easier to establish a positive reputation as a new sender, than it is to repair an existing reputation.

If you are sending a very low volume of email (less than 10,000 emails/month), ISPs will probably not pay much attention to your sending habits. However, if you are sending higher volumes, the IP warmup process plays a much more significant role in establishing your reputation. However, we recommend that all users warm up new IP addresses regardless of the amount of email they send.

How do I warm up my IP address?

The following schedule shows the automatic hourly warmup schedule and email limits that are suggested to warmup your IP addresses.

It is important to note an IP warmup plan is merely a way to help the sender identify potential weaknesses in their email program. Starting slowly gives the sender a chance to pause or slow down sending and adjust their strategy before their reputation is severely impacted.

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

 

ninjaWarm Up Guide