You've probably been told to keep your transactional emails separate from your bulk emails, but what does that mean and why should you listen to this advice?
Transactional emails are emails that your customer triggers—a welcome email after a customer signs up, an alert email a customer has set up in your app, an invoice email and a comment notification all qualify as transactional email. There are others as well, the exact nature of transactional email you send will vary according to the type of app you run.
A promotional email is an email that is sent to more than one person that contains the exact same content and is not triggered by an event. A promotional email would be anything a customer did not specifically trigger, for example a weekly newsletter, a marketing email or an announcement about your site's recent updates. Currently, Postmark does not send bulk emails like these.
To understand why Postmark doesn't send promotional emails, let's go back to that advice you may have heard—why keep these two types of email separate? In a nutshell: keeping your important transactional emails—the ones your customers are expecting—separate 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, or, 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 emails addresses for each kind of mail makes it much more likely that your important transactional email will to get to your customers.
Shared IP addresses that only send transactional emails like Postmark’s will always have a better reputation than shared IP addresses that also send promotional email.
If you use the same servers and email address to send both bulk and transactional email filtering systems like Gmail's may classify it all as bulk email. That's why Gmail officially suggests that "if you send both promotional mail and transactional mail relating to your organization, we recommend separating mail by purpose as much as possible." This helps Gmail tell the difference between the two, and it ensures the best possible reputation for your transactional email. Given the staggering number of Gmail users out there, adhering to this advice makes good business sense.
Since lost or even delayed transactional emails will result in support requests, like the familiar, "I tried to reset my password, but I never receive the email response", and more work for your organization. Then there's the potential lost customer trust. Searching through your spam folder for a legitimate email is never fun. Don't send your customers into their spam folders when there's an easy way to avoid it -- keep them separated.
So how to do you separate your mail? And what does “separate” mean? It means making sure your bulk emails comes from one source and your transactional from another, separating IP addresses, domains and possibly email addresses as well. These days reputation is increasingly shifting to domains because IPs are increasingly disposable. It’s much easier for spammers to cycle through new IP addresses than it is to cycle through domains. It also means that with more of your reputation tied to your domain, you can take it with you if you need to change providers.
For example you might send your bulk email from promo.yourdomain.com and your transactional email from trx.yourdomain.com. You could even use entirely different domains, for instance, mypromodomain.com and mydomain.com. Or you might be able to get by with just using email@example.com for bulk and firstname.lastname@example.org. However, given Gmail’s recommendation to use separate domains and IP addresses, simply using different email addresses should be a last resort.
For us this isn't just a theory. Postmark sees the best inbox rates and delivery times in the industry because we only send transactional emails. That means our IPs have great reputations that aren't bogged down by shared IP addresses that are being used to send promotional email and transactional email for a variety of providers. We police them much more strictly than the other providers who are a bit more lax about it since they send bulk mail as well. Shared IP addresses that only send transactional emails like Postmark’s will always have a better reputation than shared IP addresses that also send promotional email.
With most providers, they’ll simply recommend customers purchase dedicated IPs when customers run into delivery issues on shared IPs. We know all this because a significant number of our customers are “refugees” from the other providers. They ran into delivery problems sending both bulk and transactional from a single source and came to us to make sure their transactional emails get where they need to be -- in their customer's inbox. You don’t have to use completely separate providers, but no matter what you do, just make sure that you send your transactional and promotional emails from different domains and IP addresses.