All,

I have run across an issue after performing an Exchange migration from Exchange 2007 to Exchange 2013.  Everything is working as expected from the end user perspective except for one problem.  When a user tries to send an attachment through another application (Adobe Reader, MS Office, etc) and Outlook is open, a network authentication prompt popups and requires that users enter their domain credentials before the attachment attaches to an email.  However, when Outlook is closed it attaches as expected without requiring user authentication.

Outlook does not otherwise require any credentials when opening and users are not running in cached mode.  I am at loss for this one as it's affecting both Outlook 2010 and 2013 users and only started after their mailbox got moved to Exchange 2013.

Any thoughts?

Hi,

According to your description, I understand that network authentication prompt popups when send an attachment by another application and Outlook is open, however it works fine when do it and Outlook is closed.
If I misunderstand your concern, please do not hesitate to let me know.

Is it works fine when entry user name and password? Do you try other new PC and reproduce it?

If it works well in new PC, please try to re-configure your Outlook profile or open Control Panel\User Accounts\Credential Manager in problematic computer, then clear the remains credential and try again.

Thanks

Hi,

As per the above information and details, to solve the attachments issue, please follow these steps: -

Exchange administrators can create a Transport rules by going to Exchange Admin Center > Mail flow > Rules. 

After start to create a new rule, you can see the full list of attachments related conditions by clicking More option > Any attachments under Apply this rule if.

I hope this information will be helpful for you.
Thanks and regards
Shweta@G 

Allen,

Your interpretation of my description is correct.  To answer your questions, when users successfully enter their credentials the "Send Email" function works as expected.  I haven't tried on a new PC as of yet but will see if I can muster one up for testing.

• Edited by Micah Howard 19 hours 20 minutes ago

Goyal,

Thank you for your response.  I am not sure that this applies as the attachments themselves are not password protected (i.e. passwore dprotected zip, pdf, xls).

Ok, I think I figured out what the problem is.  This is the first migration I have done since CU7 released for Exchange 2013.  There was a public folder database that was setup on the old Exchange server that was only being used for system public folders and nothing more.  The Outlook clients were trying to connect to that PF store which naturally won't work if the coexistence isn't configured properly.  This is related to the changes Microsoft made starting with CU5 where you need to setup a proxy mb on the legacy Exchange server.  Once I followed this procedure everything eventually worked itself out.  I referenced this blog article (http://blogs.technet.com/b/exchange/archive/2014/11/07/on-premises-legacy-public-folder-coexistence-for-exchange-2013-cumulative-update-7-and-beyond.aspx).

Thanks for all of your suggestions.  Much appreciated!

• Marked as answer by Allen_WangJFMicrosoft contingent staff, Moderator 6 hours 6 minutes ago

Hi,

Thanks for your sh