Warming Up an IP Address
When adding a [dedicated IP address][sg-dedicated-ips] to your account, gradually increase the volume of email messages sent through the [IP address][]. This process is called [IP warm up][ip-warm]. This gradual process helps to establish a reputation with Internet Service Providers (ISPs) as a legitimate email sender.
When you add a 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. To establish a positive sender reputation, warm up your IP address.
When an ISP observes email suddenly coming from an added 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 factor in spam detection, begin sending a low to moderate volume. You can work your way up to larger volumes. This gives the receiving email providers a chance to observe your sending habits and record how your recipients engage with your email.
A gradual warmup doesn't guarantee a perfect sending reputation. Follow sending best practices.
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Establishing a positive reputation as a sender takes less effort than repairing an existing reputation.
To add an IP address into warm up, use the automated IP warmup feature.
If you have one or more existing available IP addresses, the added IP address email volume slowly increases over time. The warming IP stops sending when the hourly limit is reached, while the other IP addresses on the account continue to send emails.
If you do not have any other available IPs, Twilio attempts a series of quick retries, then retries approximately every 15 minutes. Emails will be retried and expire after 72 hours
If you prefer a customizable approach, use manual IP warmup. This allows you to gradually increase your email volume over your dedicated IP address.
To learn how much mail to send during the warm up process, see the Twilio recommended IP Warmup Schedule.
Automatic IP warmup allows Twilio SendGrid to throttle the number of emails for you, avoiding you damaging your sender reputation.
To set up automated IP warmup in the UI:
- Go to Settings > IP Addresses.
- Click the action menu for the IP you want to warmup. This brings up the Edit Your Dedicated IP Address screen.
- Select Use Automated IP warmup.
- Save the Edit Your Dedicated IP Address screen.
You can also put your IP address into warmup mode with the Automated Warmup API. This API throttles traffic sent through your added IP according to the warmup schedule.
Danger
When automatically warming up an IP address, SendGrid limits the amount of email sent through that IP address per hour. The IP address placed in automated warmup sends the email requests across all available IP addresses.
Note: Available IP addresses can also include other IP addresses in automated warmup with sending capacity.
The warming IP address stops sending when it reaches the hourly limit. Other IP addresses on the account continue to send email messages. If you lack other available IP addresses, Twilio retries sending the messages for 72 hours. To learn more, see deferrals.
| 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 |
Upon completion of day 41 in the warmup schedule, automated warmup removes these IP addresses.
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If you send transactional emails, don't focus on a strict IP warmup schedule. You can't control the rate at which transactional emails trigger. If you send marketing emails, follow some form of IP warmup. The slower you can warm up the better. This way, you can locate and fix any anomalies and issues that arise when you first begin sending, helping your deliverability long term.
Some [email service providers (ESPs)][esp] do not offer dedicated IP addresses to their customers - they place all of their customers on shared IP groups by default. SendGrid Free and Essentials customers leverage our shared pools and therefore don't require a warm up strategy.
Having a dedicated IP allows you to control your own reputation completely, and prevents your sending from being impacted by the reputations of other SendGrid users. SendGrid customers utilizing dedicated IP addresses are strongly encouraged to undertake a warming program in order to avoid possible deliverability challenges that may be faced when sending from new IP addresses.