I have just upgraded a user to office 356 and outlook 2013. Everything is fine except they cannot send xlsx files...they get stuck in the outbox and never send. XLS files get sent correcly as well as DOCX and PPTX but but for some reason xlsx file do not...I can send them from my outlook 2013, As well as I can see her setup is exactly the same as mine...is there a reg entry that might be preventing these files from sending

Thank you.

Hi,

Does this only happen with a particular .XLSX file or any? When the message got stuck in the Outbox, did you see any Send/Receive error?

Please have a try with a simple, new created .XLSX file, and see if issue persists.

Also, does the user have any viurs scanner integrated with Outlook? If yes, please try to disable the integration, then try again. The virus scanner will scan any emails that you send, including the attachments in it, which might cause the issue.

Please feel free to post back with any findings.

Regards,

Ethan Hua
TechNet Community Support