Domain and IP strategy

Domain and IP strategy form a critical aspect of email deliverability. This is important because:

Sender reputation is linked to a domain and IP address/s, so this is an important decision for a customer
It is strongly recommended that senders assign a separate subdomain of the main domain name for each distinct sending purpose. While the main domain can be used for corporate purposes (communication between employees, or between employees and external one-to-one contacts, for example), several different subdomains can and should be used for other sending purposes. In these cases, using separate subdomains protects company mail from the mailing practices of customers. The recommendation is to dedicate a specific use case for each of your sending domains.

For example, you can have one domain or subdomain for marketing emails, another for transactional emails, and your main domain for corporate communication. This segmentation helps you to better manage your email flows and improve deliverability. It also allows spam filters to perform quicker DNS lookups, resulting in faster and better delivery of your emails.

Additionally, using subdomains for different activities can help identify the source of any potential spam issues.

Infobip provides more detailed examples of domain and subdomain usage for your email flows.

Domain: company.com

Marketing	mkt.company.com
Transactional	trk.company.com
Support	help.company.com

By allocating specific subdomains for different email activities, such as marketing, transactional, and support, you can effectively segment your email flows within your organization. This segmentation helps streamline your email management and facilitates the identification of any potential issues with specific activities. It's a strategic approach to optimize your email deliverability.

IP strategy

IP strategy is a critical element for email deliverability. IP strategy refers to the approach and management of the IP addresses used for sending your emails. IP strategy must take into consideration shared IP addresses versus dedicated IP addresses and maintain a positive IP reputation.

All email is delivered over an IP address. Inbox providers use your IP address to judge your sending reputation when determining whether or not to deliver your email to the recipient’s inbox.
You’ll have two options to choose from with Infobip - dedicated IPor shared IP.
If you send emails less than three days a week and you send less than 5,000 emailson those days, a shared IP address is likely to be the best choice for you. With such a low send volume, you’d barely be able to keep your IP address “warm” enough to be recognized as a regular sender by the major ISPs. In this case, choose a shared IP pool.
If you are sending at least three times per week, and each time you send 5000+ emails daily, then a dedicated IP is most likely the right choicefor you! A consistent sending pattern could help you build a solid reputation on a dedicated IP address. You’ll also be able to take advantage of other services like whitelisting for improved email deliverability.

Dedicated IP

The following guidance helps you to decide whether to choose dedicated IP addresses:

You are the only sender on your IP, meaning the reputation is determined solely by your sending behavior, dedicated IP is always the best option.
If you’re a high-volume sender who wants to make sure you’re in complete control of your sending reputation, you’re going to need a dedicated IP address*. (or even a few addresses if you’re segmenting your email streams by type of email).*
A dedicated IP address can improve your deliverability rates tremendously – if your email best practices are in place and all the other parts of your deliverability equation are in place.
A consistent sending pattern could help you build a solid reputation on a dedicated IP address. You’ll also be able to take advantage of other services like whitelisting for improved email deliverability.
One of the major reasons larger companies choose a dedicated IP address is they know they’re following deliverability best practices, and they want the full benefits of that work.
You might even want more than one dedicated IP address (also separate domains). That would allow you to send specific types of email messages from each IP address. For example, your transactional emails could go out on IP address #1, and your promotional email messages could go out on IP address #2.

Shared IP

The following guidance helps you to decide whether to choose shared IP addresses:

You send emails from a server that also sends emails from other users. The IP reputation is therefore determined based on an aggregate look at all of the sending activity from all users.
If you send emails less than three days a week and you send less than 5,000 emails on those days, a shared IP address is likely to be the best choice for you. With such a low send volume, you’d barely be able to keep your IP address “warm” enough to be recognized as a regular sender by the major ISPs. In this case, choose a shared IP pool.
Establishing a reputation and history with mailbox providers can take longer if you are a low-volume sender.
Infobip doesn’t recommend using a dedicated IP if the client goes with lower volume plans. The reason is that you are not sending enough emails to manage its reputation. An IP needs to be warmed up and kept warm for effective results. A sudden burst of activity on an unused IP looks like spam to most ISPs, and they, therefore, are most likely to block your emails.

Choosing the IP strategy

Why keep the two types of email separate? There are pros and cons to using dedicated and shared IP addresses for email:

Keeping your important transactional emails (the ones your customers are expecting) separate by using different dedicated IPs makes them much more likely to land in the customer's inbox.
The reputation of the IP address, domain, and email address all play a role in getting your email into your customer's inbox rather than their spam folder. In the case of Google, one of the inbox sub-categories like "Promotional". Email providers know that customers want and expect transactional emails, but it's not always easy for them to tell what's transactional and what's better classified as promotional.
Using separate domains or IP addresses for each kind of mail makes it much more likely that your important transactional email be delivered to your customers.
You’ll need to warm up your new IP address slowly or ISPs could block your emails. This happens because, from the ISPs’ view, they saw no activity from an IP address for a while, and then suddenly there is a large volume of activity.

To help you make the right choice for your business, the following table walks you through the pros and cons of both dedicated and shared IP addresses.

	Dedicated IP	Shared IP
Choose when	Send frequently, more than 3 times per week. Send a minimum of 100,000 emails per month Timely delivery is crucial for you	Send occasional campaigns. Send less than 100,000 emails per month. Need to get up and running quickly with no time for warm-up
Pros	Reputation is determined solely by your behaviour	Already warmed up
Cons	Need IP warm-up for 6-8 weeks based on volume	IP reputation depends on all users’ behaviour

Shared IP addresses are commonly used when sending emails with low volumes and irregular sending patterns, where multiple senders share the same IP pool. However, a dedicated IP address is only used by a single domain.

It's important to note that maintaining a good IP reputation is crucial for deliverability. This reputation is influenced by factors such as sender scores and blacklistings. The information suggests that the IPs' sender score ranges from 97 to 99 points, which is considered good for shared infrastructure.

Deliverability recommendations IP/Domain warmup