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SMTP Relay Service or Dedicated IP—Which is best?

Jonathan Winters
by Jonathan Winters on November 13, 2017

SMTP Relay Service or Dedicated IP.jpg

In our digital age, reputation is key. 

If you’re like me you check and compare online reviews all the time. I check before visiting a new restaurant, choosing a new doctor or even when I’m buying a simple kitchen tool on Amazon. Chances are you've thought about how nice it might be to have access to the resources and reputation of a much bigger company. 

And in the world of email, you can do exactly that! SMTP relay services such as Amazon SES, SendGrid, Sparkpost or GreenArrow Cloud offer access to their reputation. These services can, therefore, be a very useful tool in your email sending toolbox, but they're not for everybody. Today’s post gives you the pros and cons of do-it-yourself vs. outsourcing your email.

Outsource your reputation or DIY?

By using an SMTP relay service your email is delivered by their IP addresses (your application simply hands off the email to their application). And you gain some of their reputation. By letting you send on their network with their IPs and domain names, they are vouching for your email. This can be a big boost!

With your own dedicated IP address, you have to warm up your IP address and build a reputation. Your email stands alone on its own merits without anyone vouching for it.

There are two main cases where this reputation building process can be harder than normal: (1) You are in an industry which sends a lot of spam (for example: health products, multi-level marketing, loans, dating sites, politics, etc) which makes your email look guilty by association. (2) Your email reputation or engagement stats are low or bad. In both of these cases, the boost of the SMTP relay service can be especially helpful.

In addition to easing the warm-up, the reputation of the relay service can sometimes provide an extra boost that gets your email into the Inbox. But be forewarned, this can cut both ways. If your relay service has a bad reputation (which happens), your Inbox delivery can be hurt.

The Abuse Desk

Remember I said that an SMTP relay service is effectively vouching for your email? With this upside comes a downside: A relay service will protect their reputation by terminating clients that are sending bad email, because your email affects their reputation.

Each relay service has their own definition of bad email—some are more strict than others. They will look at your complaint ratios, engagement ratios, content, and other factors to determine the quality of your email, and if it does not meet their standards they will suspend your account. If they do terminate your account, there will typically be no notice or opportunity to appeal. 

Managing Your IPs

With your own dedicated IP address you have full control over all of the technical details of how your email is sent and direct insight into all of your own delivery statistics. On the other hand, you have full responsibility for all of the management, which creates an additional layer of cost and complexity. A relay service can take care of all that for you, usually for a fee.

If you don't have the time (or desire) to manage your own dedicated IP details, relaying all of your email through a managed third-party service can remove it from your workflow. While this can mean giving up some control, as well as losing access to some of the reporting or data — if your primary focus is on your business, content, or customer relationships, then this may be the kind of delegation you're looking for. Deliverability management done by a third-party can free you up to work on your business instead of just in it.


An SMTP relay service will charge based off of your volume, so this could add significantly to the cost.

So which is best?

You probably won’t be surprised when I suggest that there is no clear winner; no single solution is right for every sender. Each business model has unique sending needs and resources — but there are two cases where a relay service makes a lot of sense. 

1) When You're Warming Up

When you are just starting out on your own dedicated IPs, there is a period of time when you’ll be warming up your IP addresses. During that time, you likely won’t be able to send your full volume of email on your dedicated IPs, which could hurt your bottom line.

Adding a Relay Server VirtualMTA into the rotation within a Routing Rule allows you the option to send the warm-up volume of email over your own IPs, and send the rest of the email via the relay service. You can warm up your IPs and send your whole volume!

2) When You Send at a Low Volume or Irregularly

It's possible you don’t send email regularly enough or you don’t have enough volume to support even a single IP address. We recommend sending a minimum of 20,000 messages per week from a dedicated IP address. When you don't have enough volume for a dedicated IP, sending through a relay service, like our own Cloud solution’s shared IP pool, can be a great option.

Sender, Know Thyself

We are often asked if GreenArrow can work with a SMTP relay service, such as Amazon SES or SendGrid or SparkPost. The answer is easy: "Absolutely—we can and we do!" The next (and best) question we’re asked is, "Should I?" Unfortunately, this answer is not as easy—there are real advantages and disadvantages either way, so it depends on what is important to you.

Things may change as time goes by. It may be that right now some combination of the two will be the best for your business, whereas down the road a dedicated IP address will be what you need (or vice versa). If you’re not yet sure what option is right for you, cloud or on-premise, or if you just have questions about how this all fits together in the big picture of your email strategy—let us know! We can walk you through it.

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Jonathan Winters
Written by Jonathan Winters
Have an email problem that needs solving or BBQ that needs smoking? Say hello to Jonathan Winters, System Administrator extraordinaire.

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