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IP address explained & basics you should know

IP addresses are at the center of email security and deliverability. But which type of IP is best for sending emails? We’ll run through the theory to the practical sides of using an IP address effectively for email marketing.

Hermes and a Goddess split email in front of colourful cabins



The internet is an essential part of modern digital life. Humans use it for almost everything, from shopping to dating to appointments. Every time you use the internet, you use an IP address. There’s a lot of talk about IP addresses, but do you know what they are? At Mailjet, we know a thing or two about IP addresses, so let’s get started.

What is an IP address?

Imagine how much easier Frodo and Sam’s journey to Mordor would be if they could send a mass email to the Fellowship? They wouldn’t need to walk so far, but they would require an internet protocol address (IP address). An IP address is a 32-bit number (or 128-bit number) used to identify hardware on your device.

Essentially, hardware connects your device to others in your area to form a home network. Your unique IP address contains your location information and allows you to transfer data over the internet or on a local network. IP addresses are necessary for the internet to differentiate between devices like routers, printers, and computers.

An IP address is a series of numbers and periods. Binary code splits it into four octets (units containing eight bits), but since binary is a jumble of zeros and ones, we convert it into dot-decimal notation. There are four sets of numbers ranging from 0 to 255, each separated by a decimal. An IP address is a hexadecimal system that might look like this: 903.177.5.332.

The Internet Assigned Numbers Authority (IANA) manages IP addresses globally along with regional internet registries (RIRs) that are responsible for local networks like internet service providers (ISPs). Your IP address serves to identify and locate your device. Now that you know what an IP address is, let’s explore what it does.

How do IP addresses work?

Your device uses an IP address to connect to a network, which allows your device to connect to the internet. Without an IP address, you have no internet. All devices in all locations follow the same guidelines: the Internet Protocol Suite. The Transmission Control Protocol and Internet Protocol are commonly known as TCP/IP and allow devices to exchange information anywhere. Much of what the TCP/IP follows initially began as a Request for Comments (RFC) in 1969, an informal collaboration of technical notes that helped build what we know as the internet today. How’s that for a history lesson?

Think of your device like a beacon, lit and ready to send and receive information on a larger network. When you want to connect to the internet, your device tries to connect to a computer network already connected to the internet.

Your internet service provider (ISP) uses the Dynamic Host Configuration Protocol (DHCP) to assign IP addresses automatically. Your company’s network accesses the internet when you use a work computer. You use an IP address whenever you access the internet, even something as simple as an app or a Facebook message.

Your ISP assigns an IP address to your device no matter where you are. You use the internet through your ISP, and they funnel it back to you through your IP address. It’s your ISP’s responsibility to provide an IP address because they grant you access to the internet. Your IP address, though always unique, can change from time to time. You can contact your ISP to change your IP address, or it may change if you turn your router or modem off. Anytime you connect to the internet somewhere else – a coffee shop, a library, a hotel – you will get a different IP address.

How to find your IP address

It’s easy to find your public IP address. Simply type into the Google search bar, “What's my IP address?” and the result will appear at the top of the page. Other websites can see your public IP address because your router has requested information from the site. You need an IP address to access that information.

Finding your private IP is a different story and depends on your device:

  • In Microsoft Windows, access the command prompt and write cmd into Windows search. In the next pop-up box, write ipconfig and the information will appear.

  • On Macs, use your system preferences to find your IP address. It should appear under your network information.

  • On your iPhone, go to your Wi-Fi settings. Click the circled i next to your network and look under the DHCP tab. Your IP address will be there.

All other IP addresses (for other devices like Android) are discovered using your router’s gateway IP address. Any attached devices should be listed when you Google your router’s unique address. Check under the “attached devices” tab, as it will list any recent devices and their IP addresses.

Which IP address fits me best?

No two IP addresses are alike. There are different types of IP address examples within separate categories, and you want to ensure you’re using the best one for your email campaign.

IPv4 vs. IPv6

Internet Protocol version 4 (IPv4) addresses were the original way for computers to connect to the internet. IPv4 addresses have since been exhausted, leading to the invention of IP version 6 addresses. IPv6 addresses allow for more combinations because the address space is 128 bits rather than IPv4’s 32 bits. Most servers, computers, and networks support both IPv4 and IPv6.

Consumer IP addresses

Anyone who uses a device that connects to the internet will have a private IP and a public IP address. A private IP works within the larger network of the public or consumer IP addresses, but each is unique. You use consumer IP addresses for large-scale email campaigns.

Private IP addresses

Devices that can connect to the internet have private IP addresses. Obvious devices like smartphones, computers, and tablets have private IP addresses, but so do Bluetooth devices like smart TVs, fridges, and speakers. That’s a lot of internet accessibility in one space, so your router will give a unique IP address to each device so the network can identify each one.

Public IP addresses

All your devices have an IP address that connects to your network, which has its own public IP address. This is what devices outside your network will recognize when they want to join. There are two forms of public IP addresses: dynamic and static.

Dynamic IP addresses

ISPs allocate a large pool of IP addresses to their customers, which automatically change. ISPs will occasionally re-use dynamic IP addresses to help reduce costs. Generating a new IP address makes it harder for cybercriminals to hack your network and makes it easier for ISPs to provide an IP address should you move house.

Static IP addresses

A static IP address is generally only used by businesses that host their own server. If you host a server, have a website, and send a large number of emails, you will need a static IP address to ensure other devices can find you on the internet. To add more fun to the mix, two types of website IP addresses exist: shared and dedicated.

Shared IP addresses

ISPs will look for consistent sending volume and consistent implementation of email best practices to determine your sender reputation. If your business sends emails on a seasonal basis or only needs to communicate occasionally, sharing an IP address is an excellent way to share the reputation of more established senders. It's also typically the less expensive option since you don’t have to pay additional setup fees for an individual IP address. Unfortunately, some senders have black-hat practices, so be careful with whom you share an IP. 

Dedicated IP addresses

If you’re using a web hosting plan, you’ll likely have the option to purchase a dedicated IP address. Acquiring an SSL certificate is easier when you have a dedicated IP address. This also means that you can share files within your organization and run your own file transfer protocol (FTP) server. An FTP server makes transmitting and receiving massive email data much easier and more accessible to everyone in your organization.

The domain name system (DNS) is a database that takes internet domain names and translates them into IP addresses. When someone searches “,” the server will map that name to the appropriate IP address.

Broadcast address

This special type of IP allows the transfer of information on all machines in a subnet rather than a single machine. This is useful for a company sending bulk emails within an internal network.

It’s important to know which type of IP address works best for your company. You’ll likely be using a dedicated or shared IP for large-volume email sending, but it’s dependent on your needs and wants.

Should I get a dedicated or shared IP?

As your business grows and you send higher volumes of email, you’ll likely want to consider moving to an individual, dedicated IP address. A dedicated IP address requires excellent email sending practices and slightly more responsibility than a shared IP address. Make sure you’ve read up on your deliverability best practices, CAN-SPAM law, and of course, GDPR.

Using your own IP address also makes it easier to track down and troubleshoot deliverability issues. You can take your campaigns one step further by dedicating an IP address to marketing emails (newsletters, promotional messages) and transactional emails (triggered messages such as thank you, birthday, and reactivation emails). Separating your traffic onto two separate IP addresses ensures that more crucial transactional emails such as invoices and account updates are not as affected by the reputation of your marketing emails.

There’s really no right or wrong answer here – it’s a matter of your business goals and how your customers prefer to communicate. We encourage customers to use a dedicated IP address to reign over their deliverability needs and sender reputation.

Most likely, you’ll get a chance to use both shared and dedicated IP addresses during different stages of your business for various types of email campaigns. The key takeaways are doing regular maintenance on your IP address, monitoring your sender score, and reviewing your deliverability reports.

Threats to your IP address

Cybercriminals will use clever tricks to steal your IP address for their nefarious deeds. They achieve this through cyberstalking and social engineering. It’s surprisingly easy for someone to track down your IP address by watching your online activity – using forums, playing video games, or checking social media. Someone could even trick you into revealing your IP address by impersonating someone you know or by the many instant messaging apps we use.

After attackers have obtained your IP address, they can commit numerous crimes with a low risk of punishment.

Hacking your device

A cybercriminal can use your IP address to hack into your device because of the ports used in the connection process. Since every IP address has thousands of ports, cybercriminals have thousands of opportunities to try to force a connection. If they hack into your device, they could steal your email lists and start spamming them, or they could install malware.

Tracking your location

If the attackers already have your IP address, then they likely know the region you live in. It doesn’t take much research to find your city, state, and home address, where they can then stalk you or rob you when you’re not home.

Downloading illegal content

Piracy is illegal and a rampant problem that’s difficult to trace. Hackers want to cover their tracks when they download illegal content, so they want your IP address to mask theirs. Piracy violates the terms of your ISP contract and may pique the attention of your ISP, the government, or law enforcement.

Attacking your network

A distributed denial-of-service (DDoS) attack is when cybercriminals use infected machines to flood a server. This influx of requests can crash the server, leading to a network shutdown – no internet for you. If you send a large batch of emails, they won’t get to your intended recipients. Your email campaign schedule will be disrupted until you have a new IP address.

Protect your IP address

Don’t worry – we’re here to help. The following tactics can help protect you from cybercriminals.

Use a VPN

A virtual private network (VPN) provides a secure network connection for your device anywhere. A VPN allows your device to act like it’s on a local network, despite you being in a different location. A VPN makes it much safer for you to use public Wi-Fi because it encrypts your communication, making it harder for hackers to steal your IP address. Try a VPN next time you’re traveling, working remotely, or when you want some privacy. 

Use a proxy server

Though not as effective as a VPN, a proxy server routes your traffic through an intermediary server. The ISPs you use will only see your proxy server’s IP address, not yours. The only downside to using a proxy server is that your chosen service might spy on you or put ads in your browser. 

Practice good privacy

Apart from VPNs and proxy servers, you should implement good privacy practices, especially in public internet spaces.

Here’s some advice:

  • Install and update a robust antivirus solution on your devices and scan for viruses frequently.

  • Never use the same password for anything. Try to make every password unique, with a combination of lowercase and uppercase letters, numbers, and symbols, rather than a phrase that already exists. This advice applies to everything in your life – your devices, accounts, door alarm code, and anything else with a password.

Don’t click on any links from unknown senders and scan the email closely. Email is highly susceptible to phishing scams, so always be alert for anything that seems suspicious. It may look like it’s from a respected business, but even one wrong letter or number in an email address is enough to trick even the seasoned security professional.

Your IP address has a reputation, and since you send emails at a high frequency, you’ll want to make sure yours has a good score. Cybercriminals will take every chance to steal your IP address, so it’s up to you to protect yourself and your email clients.

Wrapping up

Your IP address is as unique as you. It should be managed, protected, and tested to ensure your next email campaign runs smoothly. Once you establish which IP suits you, you can get to the important work – crafting excellent emails. Mailjet's dedicated API support can help with any questions about email design, delivery, and application, which (unsurprisingly) all require IP addresses.

Are you now feeling confident in your IP address choice? Your email clients (and their devices) will thank you. Mailjet salutes you and your uniqueness, so go out there and send!

A dedicated IP address with Mailjet

For high volume senders, a dedicated IP address will allow you to have full control of emails sent from your own IP, and optimize your IP reputation to help ensure your emails land in the inbox.

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