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Dynamics 365 Community / Forums / Microsoft Dynamics CRM (Archived) / Server-Side Sync (CRM ...
Microsoft Dynamics CRM (Archived)

Server-Side Sync (CRM and Exchange On-Premises) - error sending email with large attachment

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Posted on by L-A Filiatrault 130

We are currently on CRM 2016 SP2.2 (8.2.2) on-premises using Server-Side Sync with our on-premises Exchange 2010 server.

Sending emails from CRM to Exchange works correctly if the email has no attachment or a small attachment (< 1 Mb in size). Anything greater than 1 Mb in size won't make it to Exchange.

I have activated tracing on the EmailConnector server role of the async service and see the following errors:

>Error creating attachment(s) for outgoing mail item fc05b4fa-1cd9-e711-914c-00155dcdb40a.  Error Details: Unhandled Exception: System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send.

[...]

>Inner Exception: System.IO.IOException: Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host.

[...]

>Inner Exception: System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

Our incoming/outgoing email size limit are clearly greater than 1Mb. In fact, server-side sync can track an email with a 15 Mb attachment from Exchange to CRM, it just can't forward that email from CRM back to Exchange.

Anyone else experienced this issue? We're about to open an incident with MS but any ideas/advice would be appreciated. Thanks!

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  • Verified answer
    Rawish Kumar Profile Picture
    Rawish Kumar 13,758 on at

    just thinking out loud - did you try to configure gmail quickly and test if that is also giving the same issue. Because i feel its proxy server issue.

  • L-A Filiatrault Profile Picture
    L-A Filiatrault 130 on at

    That was an excellent idea, thanks Rawish. I configured using a Hotmail account since you can interface as an Exchange server profile using EWS via outlook.office365.com. I was able to send an email with a large attachment so there's most likely a connectivity/proxy server issue at play. Thanks!

  • L-A Filiatrault Profile Picture
    L-A Filiatrault 130 on at

    This article helped: support.microsoft.com/.../unable-to-send-large-attachments-using-ews-client

    Turns out our server lacked the ProxyTimeout setting and the default value for the settings seems too low to transmit large attachments. We'll be adding that key to the EWS web.config file with a adequate value.

    Thanks again!

  • Rawish Kumar Profile Picture
    Rawish Kumar 13,758 on at

    Thanks for the post - i will have a look on this and good to hear that you got it working :)

  • Community Member Profile Picture
    Community Member on at

    This is happening is with Dynamics 365 online and Exchange Hybrid (online/onpremise).  Is anyone else having this issue where you can't send an email from CRM with an attachment over 1 MB?  Mind you, we have the email size limit and performed a number of system changes recommended by Microsoft and we are still experiencing this issue.

  • L-A Filiatrault Profile Picture
    L-A Filiatrault 130 on at

    Hi RSM2CRM, in our situation, the issue was that your size limit parameters can vary according to the interface your are using. The Dynamics 365/Exchange integration uses Exchange Web Services (EWS). Check if the following parameters for EWS:

    maxAllowedContentLength

    maxReceivedMessageSize

    These could be set lower than for other ways of connecting to Exchange such as MAPI.

    It would also explain how you could use an email account and send an email with >1Mb attachment but cannot send the same email with the same account through D365.

    Good luck!

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