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Email is complicated. Hundreds of billions of messages are sent every day. Zendesk alone receives and processes millions. Over time, email's mission has changed. It's not just for person-to-person communication but also for mass mailing and machine communication. Complication introduces several threats, including mail loops, which Zendesk Support takes into account for email management.
This article contains the following sections:
What's a mail loop?
Automatic acknowledgment of messages is a common practice for software that receives email. The default trigger Notify requester and CCs of received request is one example. When a ticket is created in Zendesk Support, the user is notified by email. This kind of behavior, while common, can result in a problem when two machines email each other.
It's not a problem for machines to receive email from one another. For example, if one system receives an email from another then sends an automatic reply, that's fine. But if that system also replies automatically, this can kick off a mail loop. In this scenario, each system will continue to reply automatically to the other every time a notification is received, creating a never-ending loop until someone or something intervenes.
Loops can occur in other ways, as well. Ticket updates may come from the API, ticket sharing, an app, or a web interface. These updates can cause emails sent by trigger notifications such as Notify requester and CCs of comment update. Sometimes, those emails can cause another update, not by email, but by some other means.
How Zendesk prevents mail loops
There are several different things Zendesk does to prevent mail loops. It should be stated clearly that we can't prevent all mail loops all the time. They're a part of the ecosystem now, and we're doing what we can, but just like spam messages, they will occasionally happen.
Here are some of the measures in place to prevent mail loops:
To learn how Zendesk prevents Zendesk-to-Zendesk email loops, see Understanding how mail loops are prevented between Zendesk accounts.
Unique support addresses, not used for users
Your users contact you at your support addresses. If you use external support addresses (for example, support@mycompany.com), Zendesk Support prevents mail loops by disallowing users with one of your support addresses as their email. In other words, if you have an end-user whose email address is support@example.com, you cannot enable support@example.com as a support address. If you have support@example.com as a support address, you cannot create a user with that address.
We do this to prevent notifications being sent to your support addresses. If we did send email to one of them, they would automatically forward that email back to Zendesk Support, creating another ticket. This process would continue to loop, resulting in many tickets or comments.
Bulk mail and no-reply addresses do not create tickets
Certain emails don't create tickets by default, such as bulk mail or messages that identify as machines.
Tickets also aren't created when the sender is a no-reply address. These are mostly governed by suspended tickets. You can add the address to the allowlist if you know the sender is safe; however, doing so will increase the rate limits for that specific email address and the number of suspensions by a factor of ten. At that point, Zendesk will start to drop the traffic. Zendesk reserves the right to suspend or block any traffic exceeding safe levels. The email channel isn't designed for programmatic or automated traffic; that is the exclusive purpose of the API. Using the email channel for this type of traffic should be regarded as a temporary workaround.
When a ticket is created on behalf of a bulk sender, Zendesk suppresses automatic notifications. Agent comments will still trigger notifications, but to avoid mail loops, Zendesk suppresses any message that is sent when no comment is added. This is true when you recover these messages from suspension or add such users to the allowlist.
Fall-back limitations for ticket updates by a user within an hour
As a last resort form of prevention, Zendesk limits the number of updates a single user can make within an hour. There's a limit of 20 emails from the same user within an hour. Beyond that, the following 20 updates will be suspended. If more than 40 are received, all additional updates within that hour will be rejected (meaning they won't even create suspended tickets). This serves as a way to prevent mail loops from becoming a serious problem.
This limitation won't work if the other system doesn't use the same email address every time. Some systems use a new email address for each automated message.
You can add the address to the allowlist if you know the sender is safe; however, doing so will increase the rate limits for that specific email address and the number of suspensions by a factor of ten. At that point, Zendesk will start to drop the traffic. Zendesk reserves the right to suspend or block any traffic exceeding safe levels. The email channel isn't designed for programmatic or automated traffic; that is the exclusive purpose of the API. Using the email channel for this type of traffic should be regarded as a temporary workaround.
24 comments
Julie Guno
Hi, how can we avoid getting 2 tickets with the same subject and same message from a sender with no-reply address?
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Shawna James
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Justin Clute
Hello,
We have a large number of customers that will contact us by sending in 20+ emails with emails that will be mostly the same except for identifying information like customer names and serial numbers. Otherwise most of these emails are word for word the same. They'll be able to get about 20 emails through before it starts dumping the remaining tickets into our suspended queue.
Adding to the allowlist does fix the issue but it would be great if there was a way to allow exceptions to the spam policy similar to the sorting methods that Zendesk uses for Triggers. While we have a reactive solution, it would be nice to have a more proactive one.
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Brett Bowser
If you're having legitimate emails go to your Suspended view I would recommend reaching out to our Customer Support team as mentioned in the article I linked.
They should be able to dig into this and figure out the cause.
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Robert Kehoe
Is this still an issue almost two years later? We're getting tons of customer emails routed into our Suspended Tickets. That is a deal breaker for us.
EDIT: Adding the customer email to the Allow List appears to have fixed the problem for us. But I'm still not clear why Zendesk started blocking the messages in the first place when we previously were receiving them. Thanks for the reply Brett.
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Sonali Maunick
Hi. We have customers that regularly exceed the 20 emails in an hour limitation and at times exceed the 40 emails an hour. We would like the ability to either change the number of emails we allow through and/or whitelist domains as we can with other suspended tickets rules.
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Sylvia King
Commenting here to add that the Fall-back limitations for ticket updates by a user in an hour rule has consistently been a pain for our company. As we grow, we have customers and suppliers that will often send over 40 emails in the span of an hour (Fedex.com notifications, for example). We spend many man-hours recovering these suspended tickets and it often results in delayed information, which impacts our customers' experience. I really hope there is a fix in the pipeline that allows us to "whitelist" certain domains that can be excluded from this email loop rule.
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DJ Buenavista Jr.
Thank you for the update. We don't have any information as of the moment, but you can get an update or information if you can post this as product feedback.
Kind regards,
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Chris Stewart
Hi DJ Buenavista Jr. - Are there plans on the roadmap to address this? If ZD is able to identify and update the ticket with the message, then you should also be able to able to feed this info elsewhere ... like add a tag for example.
9 times out of 10 these auto-reply messages would have been filtered as spam if they originated outside of ZD, so it is strange that you have chosen to prioritize and force these into people's instances.
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DJ Buenavista Jr.
Thank you for reaching out to Zendesk Support.
In regards to your concern, unfortunately, at the moment it cannot be selected from the conditions available inside the triggers. The following flag that was mentioned in the article is hard-coded into our system, and unfortunately cannot be defined right now in triggers/tagging. The triggers that were mentioned in the statement above refer to the existing and available "Received at" trigger condition which is defined by selecting the specific support email address.
I would highly encourage you to post this as product feedback on our Zendesk Support Feedback page.
Thank you and have a wonderful day ahead!
Kind regards,
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