In custom SMTP environments, email processing can slow down when groups and distribution lists aren't set up correctly. You'll often see this first in high-volume assignment groups, like helpdesk or IT support teams, that receive frequent notifications when records are assigned.
This may also be evidenced by:
- Sluggish email processing or spikes in outbound queue processing times
- External distribution group members not getting emails
- Undelivered email or delivery failure notices
Let’s review how email groups can impact email processing and how to resolve inefficient group configuration.
| Who this is for - ServiceNow admins - Platform owners - Email or messaging admins who manage SMTP servers, gateways, or Office 365 / Exchange - Anyone troubleshooting delayed notifications from ServiceNow |
Why correct group email configuration is important
In general terms, groups facilitate team communication and enhance collaboration, with a central workspace, shared inbox, calendar, and document library. Distribution lists, on the other hand, are specifically suited for one-to-many communications, such as all-company notifications and newsletters. While both types of emails go through the same process in your email stack, a misconfigured email group with a large number of recipients can cause significant delays.
With group emails, your instance may process an email with multiple recipients one at a time before sending to your custom SMTP server. This serial processing can quickly multiply the send time. For example, if your instance sends an email with 100 recipients, and it takes 100 ms to send each recipient command to your SMTP server, it will take about 1.5 minutes (100 × 100 = 1,000 seconds) just to add all recipients. At a rate of 1 command per second, this means a group email to 100 recipients could take over 15 minutes to process and also delay other emails in the queue.
Additional steps, such as validation and other security screening tools, can further delay processing.
Steps to resolve group recipient configuration issues
1. Check if your groups have a group email set up.
2. If so, verify that Include Members is not selected unless necessary.
- Go to:
/sys_user_group_list.do?sysparm_query=emailISEMPTY%5EORinclude_members%3Dtrue%5Eactive%3Dtrue&sysparm_view=
3. For groups with more than 20 members and no group email:
- In your email system, create a distribution list.
- Use that distribution list email as the group email
- To check affected groups:
/sys_user_grmember_list.do?sysparm_query=group.include_members%3Dtrue%5EORgroup.emailISEMPTY&sysparm_view=
3. Ask your email administrators to do one of the following:
- Turn off recipient validation for the email account. Email administrators may not be willing to turn off validation due to security concerns. Validation can take 100 ms to 10 seconds per recipient depending on the email system.
- Add the distribution list to the allow list used by your instance. This marks the list as trusted and truncates processing time.
4. Check for scheduled reports with many recipients (users, groups – especially those without group emails – or email addresses) that run during business hours:
- To check, go to:
/sysauto_report_list.do?sysparm_query=active%3Dtrue%5Erun_type%3Ddaily%5EORrun_type%3Dperiodically
Wrap up
There are many factors that can cause sluggish email performance in a custom SMTP server environment. Group emails can cause significant delays in processing when not configured efficiently. Using trusted distribution lists can reduce processing time and ensure a smoother experience.If your group emails and distribution lists are configured appropriately and processing is still slow, your server may not be able to handle the volume of emails from your instance. Check out this article on how to troubleshoot slow emails when using a custom SMTP server.
Additional Resources
- Troubleshoot slow outbound email processing with custom SMTP servers
- How to use Preview Notification to troubleshoot undelivered emails
- Verify a user's email notification preferences
- Email and SMS notification
- Email diagnostics dashboard
Now the most important question: Is this article helpful?
