Emails not being delivered, or being delayed in delivery, can cause end users a lot of frustration. Most Administrators will have received support calls where end users have either received a postmaster notification (NDR – Non‐Delivery Report), or when an email has not been received or delivered.
As an email Administrator, it is crucial to be able to troubleshoot these queries, and determine why email delivery was delayed or has failed. Alternatively, for emails that have been successfully delivered, having the ability to search for an email and review the emails' headers and transmission details allows you to prove delivery or chains of custody.
Using the information available from the end user and Mimecast’s viewers and queues can vastly decrease the amount of time spent determining what happened to an email. It is important to note that Mimecast logs all connections whether successful or not.
Troubleshooting Scenarios
When troubleshooting email delivery, it is helpful to group these queries into scenarios - failed or delayed delivery which can apply to both inbound and outbound emails:
Outbound Email
An outbound email not being delivered could be a result of either a failed or delayed delivery of the message. Follow the troubleshooting steps below to determine why the email has not been delivered:
- Obtain as much information as possible regarding the email e.g. sender and recipient, date and time the email was sent. Try and establish if the sender received an NDR or postmaster notification
- Navigate to Gateway | Tracking and perform a search based on the information obtained above
- From the results, select the email in question, and analyze the additional information provided
Below are the possible viewers and queues, and email troubleshooting scenarios:
Failed Delivery
| Bounce Viewer | Accepted by Mimecast, but cannot be delivered to next hop mail server. Typical reasons for the bounce could be due to an incorrect recipient email address, or if the email has a large attachment |
| Accepted Emails or Archive Search | Email has been accepted by Mimecast, and delivered to the next hop, however there may be a failure further along in the delivery of the email. Delivery of the email can be confirmed by reviewing the delivery transmission data of the message |
| Delayed Delivery | |
|---|---|
| Delivery Queue | Email is currently queued on delivery retry. If the recipient's mail server is not currently accepting email or their DNS hosting service is experiencing issues, emails will be queued on retry |
| Accepted Emails or Archive Search | Email has been accepted by Mimecast, and delivered to the next hop, however there may be a delay further along in the delivery of the email. Delivery of the email (including date/time) can be confirmed by reviewing the delivery transmission data of the message |
If this email does not show in Tracking, it could be that your internal mail server has not yet delivered the email to Mimecast, or bounced the email.
Inbound Email
An inbound email not being received could be a result of either a failed or delayed delivery of the message. Follow the troubleshooting steps below to determine why the email has not been received:
- Obtain as much information as possible regarding the email e.g. sender and recipient, date and time the email was sent. Try and establish if the sender received an NDR or postmaster notification.
- Navigate to Gateway | Tracking and perform a search based on the information obtained above
- From the results, select the email in question, and analyze the additional information provided
Below are the possible viewers and queues, and email troubleshooting scenarios:
| Failed Delivery | |
|---|---|
| Rejection Viewer | Rejected by Mimecast in protocol. This is typically based on the sender's details (email address, or IP address) or content of the email |
| Bounce Viewer | Email has been accepted by Mimecast, but your internal mail server has rejected the email |
| Accepted Emails or Archive Search | Email has been accepted by Mimecast, and delivered to the next hop, however there may be a failure in delivering the email internally. Delivery of the email can be confirmed by reviewing the delivery transmission data of the message |
| Delayed Delivery |
|
|---|---|
| Held | Email has been placed on hold due to a content scanning policy. This could be a Spam Scanning, Attachment Management or Content Examination Policy |
| Connection Attempts | The email has been subjected to additional checks (temporary failure) and is typically as a result of greylisting, or a realtime reputation check |
| Accepted Emails or Archive Search | Email has been accepted by Mimecast, and delivered to the next hop, however there may be a delay in delivering the email internally. Delivery of the email (including date/time) can be confirmed by reviewing the delivery transmission data of the message |
If this email doesn't show in Tracking, it could be that the email was rejected prior to Mimecast.
Proving Email Delivery
There may be occasions when you need to prove that an email was delivered, confirm the mail servers involved, as well as determine the date and time the email was delivered by Mimecast.
Follow the steps below to confirm the delivery details for a message:
- Obtain as much information as possible regarding the email e.g. sender and recipient, date and time the email was sent
- Navigate to Accepted Email OR Archive Search (depending when the email was sent) and perform a search based on the information obtained above
- From the results, select the email in question, and analyze the transmission information provided. This includes reviewing the receipt and delivery view, as well what policies were applied to the message.
Depending on when the email was sent will determine which viewer should be searched:
| Viewer | Description |
|---|---|
| Accepted Email | Emails can remain in Accepted Emails from anything between 2 to 6 hours, and during this time, messages are compressed, encrypted, indexed and then moved to the Archive. Alternatively an email may remain in Accepted Emails until it reaches it’s final state, which is either considered as successful delivery or a failed delivery |
| Archive Search | Once emails have been indexed, de-duplicated, compressed and encrypted, they are moved to the Mimecast storage grid and archived. Using Archive Search Administrators are able to trace emails and troubleshoot email delivery. |
Carlos Rios
Comments