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Since last update (26.3) mails stuck in outbox

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Posted on by MG-31070844-0

Hi All,

Since the last update to v26.3 mails sent from Business Central are stuck in the mail outbox. They stay on status Pending. Some emails are being sent but stay in outbox with status processing.

It happens with different users, different emailaccounts and even different tenants. Does anyone else have an issue with mails going out since the last update? We tried to find a good scenario when this happens, but it seems random and it looks like the emails are stuck after hitting a threshold of some sort. I personally think it has to do with the new fields added on the Email Accounts page: Email Rate Limit and Email Concurrency Limit.

With kind regards,

Michael Glashouwer

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Dynamics 365 Business Central

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CC-08081413-0 on at

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Since last update (26.3) mails stuck in outbox

Deleting the "In progress" worked for me.

Thanks MG-31070844-0

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DAnny3211 Moderator on at

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Since last update (26.3) mails stuck in outbox

Hello,

Following the update to version 26.3 of Business Central, the issue reported with emails remaining in the Outbox with status Pending or Processing may be related to the introduction of two new fields on the Email Accounts page:

Email Rate Limit

Email Concurrency Limit

These fields are designed to control the number of emails sent within a given time frame and the number of concurrent email processes. If not configured appropriately, they may cause emails to remain stuck in the outbox.

Suggested Actions:

Review the values set for Email Rate Limit and Email Concurrency Limit. In environments with high email volume, overly restrictive values may create bottlenecks.

Test with increased limits, for example setting the rate limit to 100 and concurrency to 10, to observe whether the issue improves.

Check system logs for any errors or timeouts related to the email sending process.

Verify SMTP or Microsoft 365 configuration, to rule out external provider limitations.

Monitor official updates from Microsoft, as this is a recent change and may be subject to further adjustments or fixes.

Kindly confirm if this resolves the issue by marking the response as accepted, so it may assist other users facing the same problem.

Best regards.

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MG-31070844-0 on at

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Since last update (26.3) mails stuck in outbox

Some extra info: When you delete the "In Progress" records and you have a lot of "Pending" records that are being send out, you sometimes get this error message: You are not authorized to access this resource: https://graph.microsoft.com/.default. Contact your system administrator.

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MG-31070844-0 on at

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Since last update (26.3) mails stuck in outbox

Thank you for all your replies!

I did some research myself: The problem is that there are too many records on status "in progress". It reaches the maximum limit of 10 records "in Progress" and then it put all the other mails that need to be send out to status "Pending". If you delete the "In progress" records then the other mails with status "Pending" will be send out, until the maximum of "in progress" records are being reached again. I have no idea why these records stay in status "in progress" and dont fail eventually. It also seems that the "in progress" mails are sent out, but just stay in the mail outbox.

Please keep me informed if there are any new updates on this issue. For some reason I cant login in yammer.

My suggestion for now would be to delete the "In progress" mails, because they are sent out and after that the rest will send too. But it is really a shitty job to do when managing multiple tenants :(

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YUN ZHU Super User 2025 Season 2 on at

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Since last update (26.3) mails stuck in outbox

The fields you mentioned were added in Business Central 2022 wave 2 (BC21) and should not be a problem.

There is a similar issue in the BC Yammer Group, which seems to be a standard Microsoft issue. You can check the discussion below.

https://www.yammer.com/dynamicsnavdev/threads/3426033489567744

Thanks.

ZHU

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Mansi Soni Super User 2025 Season 2 on at

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Since last update (26.3) mails stuck in outbox

Hello @MG-31070844-0,

Hope you will get some hints with this resources!

https://yzhums.com/32813/
https://learn.microsoft.com/en-us/dynamics365/business-central/admin-how-setup-email
https://learn.microsoft.com/en-us/dynamics365-release-plan/2022wave2/smb/dynamics365-business-central/easily-comply-email-sending-limits-through-email-throttling
https://learn.microsoft.com/en-us/troubleshoot/power-platform/dataverse/email-exchange-synchronization/errorquotaexceeded-exchange-server-returned-403-error

Regards,
Mansi Soni

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Sumit Singh on at

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Since last update (26.3) mails stuck in outbox

The email screenshot you provided from Business Central highlights a key issue:
"Your emails are being throttled due to the rate limit set on an account."
This message, along with the statuses shown in the outbox—mostly "Pending" and some "Processing"—strongly suggests that the new Email Rate Limit and Email Concurrency Limit fields introduced in version v26.3 are actively throttling outgoing emails.
Here's what this likely means:

Email Rate Limit: Controls how many emails can be sent per minute/hour.

Email Concurrency Limit: Controls how many emails can be processed simultaneously.

If these limits are set too low, Business Central will queue emails and delay sending, resulting in the "Pending" or "Processing" statuses you're seeing.
Recommended Actions:

Check the Email Account Settings:

Go to Email Accounts in Business Central.

Review the values for Email Rate Limit and Email Concurrency Limit.

If they are too restrictive (e.g., Rate Limit = 10 emails/minute), increase them based on your expected volume.

Monitor Email Queue Behavior:

After adjusting the limits, monitor the outbox to see if emails start clearing more quickly.

Check for Background Task Failures:

Go to Job Queue Entries or Email Outbox logs to see if any background tasks are failing or retrying.

Microsoft Documentation or Support:

Since this issue spans multiple tenants and users, it may be a broader issue introduced in v26.3. Checking the Microsoft Dynamics 365 release notes or raising a support ticket could provide confirmation or a hotfix.

Note: This response was created in collaboration with Microsoft Copilot to ensure clarity and completeness. I hope it helps to some extent.
Mark the Answer as Verified if this is Helpful.

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