While distribution lists can seem like a more efficient way to send emails, they can cause more trouble than they’re worth when sending through a bulk SMTP relay like Oracle Cloud Infrastructure (OCI) Email Delivery.

For the uninitiated, a distribution list, also referred to as a group or an alias is when you send to an email address that then distributes that message to anyone on that list, commonly used in large companies, such as company-employees@companyx.com. Instead of the list admin needing to input every address of a list member manually, they create one email address and send to that, covering everyone they need to contact.

Easy, right? Not quite.

A single point of failure

A distribution list (DL) address still works like any other email address: One email address sends to another email address, and the receiving mail server accepts the message. With a DL, that address you’re sending to then distributes the email to whatever number of email addresses are on the DL. But that number of addresses means that many opportunities for a hard bounce, which then causes a suppression. A hard bounce from a DL address means that the whole DL address is bounced, not just the member of the list that causes the suppression.

For example, Jane Smith leaves Company X and her email address was jane.smith@companyX.com. Jane was on an internal DL, which had 92 other employees on it. The admin of the DL doesn’t remove Jane’s email from the list, which gets deactivated by the IT team. The next time that the team lead attempts to send to the list, the DL address hard bounces and no one gets the email because Jane’s inactive address is still on it.

Potential solutions and ideas

We have some options to work through these problems. The most obvious way is to not send to DLs through bulk SMTP relays like OCI Email Delivery. Because of the upkeep involved with DLs, often even the most diligent sender has a problem at some point. Distribution lists are better served in personal correspondence because of the level of maintenance needed otherwise.

An easy option is to simply create a mailing list versus using a DL. With the list, each address is sent to individually and not through a DL, so if there’s a hard bounce, it affects only that address and not every other email. A DL admin can also continually maintain their list. But if they miss a single address that becomes invalid, a suppression occurs.

If you can’t use these options and absolutely must use an SMTP relay for your DLs, set up alerts for suppressions, so when your DL inevitably gets added, you know that an issue exists and can work with your IT team or HR to figure out who’s no longer there, what address is misspelled, and so on.

Final thoughts

Maintaining distribution lists can be a pain, especially in larger companies. While they’re necessary for many reasons, using SMTP relays to send this email can often add more work than intended. Knowing why DL addresses get suppressed, knowing how to work through the problems, and finding alternatives in sending is a step toward ensuring that important emails get to who they’re supposed to when they’re supposed to.