When you create a new SMTP server With a new dedicated IP address like we provide, before you can start sending email marketing campaigns you need to "warm up" your IP address.

Additionally, you need to "warm it up" if you've left your IP address without sending an email for more than about 30 days.

So, SMTP warmup is somewhat of a continuous process.

What is "warming" an IP address

When you have a new IP address for your SMTP, that IP address will have no reputation on the Internet and ISPs (Internet Service Providers) do not know about that IP address. IP warming is the practice of building your reputation on the Internet by gradually increasing the volume of mail sent with your IP address on a predetermined schedule.

When an ISP notices an email suddenly coming from a new IP address, it immediately begins evaluating the traffic coming from that IP address.

Since ISPs consider email volume as a key to determining spam, it is best to start sending a low volume of emails and then gradually increase to larger amounts.

This gives email providers a chance to carefully observe and analyze your sending habits and volumes and record how your recipients interact with your email.

Typically, warming up takes between 1 and a few weeks depending on your scenario and the number of emails you want to send per day.

How do ISPs evaluate your emails and reputation?

When you start the warm-up process, ISPs will evaluate your reputation based on three main factors:

• Bounce rate: When sending an email campaign, you need to make sure that your emails are valid. A high bounce rate will destroy your reputation.
• Spam traps: even a very small percentage of spam traps can get you blacklisted!
• Spam content: The content of your message is essential; ISPs will check if you use spammy keywords or blacklisted links.
• User Interaction: how recipients interact with your emails, if they report you as spam, then it's a real problem!

Email Volume and Timeline

The number of emails you send depends on your own total email volume, some may require sending 100 emails per day, and others may require 1 million per day!

You need to send enough emails at a sufficient frequency so that your email reputation can be tracked.

Also, you should know something very important: most reputation systems only store data for 30 days, so you should not go 30 days or more without submitting an IP address. If you do, you will have to warm it up again.

The simplest 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, based on this calculation. For example: if you send 90,000 emails/month, you should start by sending 3,000 per day for the first month, and so on.

Keep warming up on ALL ISPs

It is important to remember that you must maintain a constant volume throughout the warm-up period for each ISP.

So remember to divide your warm-up schedule so that each ISP gets a comparable amount of mail each day. Don't warm up Gmail on Monday, Yahoo! on Tuesday, etc.—distribute your mail evenly to each ISP on each warm-up day.)

Otherwise, your sending activity will appear sporadic and you won't be able to build a solid reputation.

Tips for your SMTP server

There are some crucial tips you need to follow while warming up the IP:

• Never start before you have a high sending score: ensure this by setting up SPF, DKIM, rDNS etc.
• Never send promotional emails during the warm-up period. You need the highest engagement rates, so send transactional emails or maybe valuable information.
• First send an email only to your top active subscribers. Ensure a bounce rate close to 0 %.
• Do not rotate or change IP addresses while warming up. Rotation is a sign of spam.
• In your emails, include a clear link for people to unsubscribe.
• Add an email signature that makes your emails look trusted.
• Send to your friends list and ask them to mark you as non-spam and tell them to reply.
• Do your best to build an audience and warm up with that audience. This way you will get the best interaction with the user and make the "warming up process" much easier.
• Monitor your campaigns accurately and make sure to keep your bounce rate below 2 % by validating your emails (for example, use the service https://debounce.io/)

How to monitor reputation?

Having the right tools to check IP reputation is halfway to success. Here are some tools and services you can use:

• Senderscore.org by Return Path The score ranges from 0 to 100, with 100 being the best. It tells you how you are performing. Typically it is recommended to keep your sender score at 90 or above.
• Senderbase.com by Cisco It tells you how your reputation is across all Cisco managed network providers. The reputation score is grouped into Good, Neutral and Bad.
• Postmaster.live.com Microsoft's Intelligent Network Data Services provide you with information about traffic originating from your IP address such as the volume of emails sent, complaint rates and spam trap hits.
• Postmaster.google.com Provides access to your domain data on Google Search Console.
• Postmaster.aol.com Check your IP reputation and rate it as “bad”, “neutral” and “good”.