Hi

I have a lot of 1040 errors in the application event log, and mail flow doesn't really always work as expected. Most of the time
there is no problem, but sometimes sending emails remain in the outbox, and are sent only after a while.

I found that this happens, when there are a lot of emails with attachments bigger than 2mb, and I think it that case its an expected behavior, isnt it? But I also see this error during the night, when there is no mail flow (according to message tracking).

This is a virtualized exchange 2013 server running on Hyper-V with all the roles on it. The server has 6 cpus and 24gb ram, and hosts only about 200 mailboxes.

During searching the internet for a solution someone recommended to set the following values:

Set-TransportService MaxConcurrentMailboxDeliveries 50 (default 20)
Set-MailboxTransportService - MaxConcurrentMailboxDeliveries 50 (default 20)

Can anyone tell me if these settings are ok?
What are possible reasons for this error and what can I do to solve this mail flow issue?

Regards
Peter

• Edited by PeterN22 Thursday, June 11, 2015 6:51 AM

Hi Peter,

You can set these values only when you get 4.2.0 errors in the mail submission queue 

Set-TransportService MaxConcurrentMailboxDeliveries 50 (default 20)
Set-MailboxTransportService - MaxConcurrentMailboxDeliveries 50 (default 20)

There could be many reasons why the emails are stuck in outbox . Its better we will analyze few things before changing these values 

1) Filter the app logs during this time and see if you are getting any errors during this time.

2) Open  up the queue viewer and see if you have emails pending in the queue. If there is just check if you get any last error message.

But if you get this alert even in the night there might be some problematic mailbox which is troubling the mailbox transport submission service to hung.

When the issue occurs please check the state of the submission service.

Also check if any emails with large attachments are stuck in the queue by running the below command 

Get-mailbox -Resultsize Unlimited | get-mailboxfolderstatistics -folderscope outbox |fl identity,ItemsinFolder,FolderSize > C:\output.txt

Hi,

This issue might be the Mailbox deliveries throttling is low. And The MaxConcurrentMailboxDeliveries parameter specifies the maximum number of delivery threads that the transport service can have open at the same time to deliver messages to mailboxes.

We can increase this value to check if it helps.

Best Regards.

Thanks to both of you for your answers.

I will check your suggestions and Keep you updated.

Regards
Peter