While storing an email with attachment the following error occurs:  

value cannot be null. parameter name:filename

It is not possible to store the email with attachment.

This behavior only occurs, if in the Connect to Outlook configuration "Attachments only" is chosen as "Storage type" and the user changes this option during the storing process in the store dialog, because the user wants to store the email and the attachment.

To sove this, please change your Connect to Outlook configuration, instead of "Attachments only" , "Email and Attachment" should be used as "Storage type". After this change the message will not occur anymore, even if the user changes the "Storage type" during the storage process, it is possible to store the email.