Third Party Email Service Rate Limits
It is generally discouraged to use your personal or corporate email server (service) to send transactional or bulk emails. The reason for this (primarily) is almost all of these types of services implement sending rate limits.
What are rate limits?
Rate limits are caps for how many emails that can be sent through the mail service in a given time-frame. There are typically several tiers of limits such as maximum messages per day, per hour, and even per minute. Here are a few examples of known rate limits at the time this article was written.
- Office365 (source)
- 10,000 recipients per day.
- 30 messages per minute.
- Gmail Suite (source)
- 2,000 messages per day
- Total recipients per day: 10,000
- External recipients per day: 3,000
- Unique recipients per day: 3,000
Note: Every email service will have their own sending rate limits, so check your service's help documentation to see what those are.
In the examples listed above, you can see immediately that there are going to be potential issues with Office365 in a high-volume scenario. You can quickly and easily reach the 30 messages per minute limit when sending out scheduled invoices, account summaries, past due notifications.
Our mail service is multi-threaded and multi-tiered. Thus, it will pull queued emails quite rapidly and begin sending them as soon as they are queued.
Note: At the time of writing this article, a new enhancement is being added to the email sending microservices that will allow for x number of sending retries. This is being done to mitigate the sending rate limitation of third party services, as we do not know how these limits will change in the future. Adding our own throttling would be very difficult to implement as we would have to set this specifically for each portal and/or third-party smtp service.
Our own internal email sending system is quite robust and includes insights like delivery reports, bounce reports, open rates. This is the recommended way to send your transactional and notification emails. However, if you still want to send through a third-party service, the recommended solution would be to utilize a third-party bulk sending service like:
GoToMyAccounts does not have any affiliation with these third-party services. These are just examples of the most popular services out there today. These services have high rate limits and are designed specifically for both transactional and bulk email sending. They also provide good reporting features. However, understand that when using a third-party sending service, you will have to look at email delivery reports inside their app or portal. When using the GoToMyAccounts sending service, delivery reports are shown right inside your email log.