Warm up my IP address

How do I warm up my email server IP address?

IP address warming is a gradual process that happens over a period of time. The aim of warming up an IP address is to establish trust and good reputation with the ISPs (Internet service providers) as a sender of legitimate, high quality emails at volume.

Warming up your IP address is the time to take a careful look at every aspect of your email marketing process, including your aims and goals. You should be able to make tweaks that will improve your overall long-term results, not just during the warm up.

Please note though that a structured “introduction” of your email server to the world while ramping up your sending volume does not guarantee trouble free sending of emails forever. You will need to play by “the rules” and utilize good list-hygiene practices.

Why do I need to warm up my IP address?

In short, too many emails that get sent are spam (unwanted emails) and the ISPs want to protect their users from receiving unwanted emails.

As a result, ISPs treat any new IP address that sends emails with skepticism. The ISPs only reduce that skepticism once the sender has proved their reputation.

What do ISPs expect from email senders?

The ISPs build up a ‘sender score’ for IP addresses and domain names based on metrics that differentiate legitimate emails from spam. These include:

Send volume
Spam complaints
Messages sent to unknown users
Subscriber engagement
Spam trap hits

… and more.

To start with, an IP address has a neutral sender score. Every time someone hits the spam button, or you get a hard bounce, or your email is sent to an unknown user, your credit rating goes down.

How do I get a good email sender reputation?

• Follow best practices
• Make sure your DKIM, SPF, Sender-ID, and Domain Keys are set up properly:


• Comply with the CAN-SPAM Act and other international anti-spam laws
• Only send to people who have opted in to receive emails and confirmed their request
• Do not buy lists from email brokers
• Avoid including large attachments and certain attachment types (.exe, .zip, .swf, etc. should be avoided)

So, how do I warm up my email server IP address? This is how to do it: 

The goal is to build up approximately 30 days of sending history so that ISPs have an understanding of the type and quality of emails being sent by your new IP address. The warm up ramp-up period may take longer than 30 days for some senders and can be less for others.

The basic approach is to estimate your total monthly email volume and divide that number by 30. Then try to spread your sending evenly over the first 30 days.

For example, if you will send 90,000 emails per month, you should start off sending 3,000 per day over the first month. Or, if you typically send about 300,000 emails per month, warm up your IP address by sending 10,000 emails per day for the first month.

For larger numbers (i.e., sending 500,000+ emails per month), you will need to extend the warm-up period to possibly over 2 months. You can also consider incremental increases to your daily send volume (e.g., 3,000 for 4 days > 4,000 for 4 days > 5,000 for 4 days > 7,500 for 4 days > 10,000 for 4 days, and so on).

There are no hard and fast rules but here are some guidelines:

• Send first to your best, most active customers
• Send consistently (having a consistent email volume from one day to another is much better than having a large volume sent on one day of the week and no email sent on the remaining days)
• Start with a hundred or so messages an hour
• Increase the hourly rate gradually
• Monitor your logs
• If the ISPs start sending back 4xx failures, you are going too fast, so slow down

Other hints and tips

• Split large, non-time-sensitive sends over a number of days
• Split campaigns between your new IP address and your legacy email system
• Create non-time-sensitive campaigns (e.g., subscriber surveys) to use specifically for the purpose of ramping up new IP addresses

Reputation Monitoring Sites:

Sender Score – https://www.senderscore.org/
Sender Base – http://www.senderbase.org
Cyren IP Reputation Check – https://www.cyren.com/security-center/cyren-ip-reputation-check
Barracuda Central – https://www.barracudacentral.org/lookups/
Spamhaus – https://www.spamhaus.org/
Microsoft SNDS – https://postmaster.live.com/snds/