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 email at volume.
Warming up your IP address is the time to take a careful look at every aspect of your email marketing process, including the aims and goals. You should be able 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 of your sending volume does not guarantee trouble free sending of email for ever more. You will need to play by ‘the rules’ and utilise good list-hygiene practices.
Why do you need to warm up an IP address?
In short, too many emails that get sent are spam (unwanted emails) and the ISP’s want to protect their users from receiving unwanted email.
As a result ISPs treat any new IP address that sends emails with scepticism. The ISP’s only ‘reduce’ that scepticism once the sender has proved their reputation.
What do ISP’s expect from email senders?
The ISP’s build up a ‘sender score’ for IP addresses and domain names based on metrics that differentiate legitimate email from spam. These include:
- Send volume
- Spam complaints
- Messages sent to unknown users
- Subscriber engagement
- Spam trap hits
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
How do I warm-up my email server IP address?
The goal is to build up approximately 30 days of sending history so that ISPs have an understanding of the type and quality of email 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.
Example: if you will send 90,000 emails/month, you should start off sending 3,000 per day over the first month.
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 week
For larger numbers i.e. sending 500,000+ per month you will need to extend the warm-up period, possibly over 2 months. You can also consider incremental increases to your daily send volume. e.g. 3k for 4 days, 4k for 4 days, 5k for 4 days, 7.5k, 10k etc etc
There are no hard and fast rules but there are some guidelines:
Send first to your best, most active customers.
Send consistently. Having a consistent mail 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 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’re going too fast so slow down.
Other hints and tips.
Splitting large, non-time-sensitive sends over a number of days
Splitting campaigns between your new IP address and your legacy mail system
Creating 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 – http://senderscore.org
Sender Base – http://senderbase.org
Cyren IP reputation monitor – http://www.cyren.com/ip-reputation-check.html
Barracuda Central – http://www.barracudacentral.org/lookups/
Spamhaus blocks – http://www.spamhaus.org/
Microsoft SNDS – http://postmaster.live.com/snds/