I have noticed this several times before. Finally want to look into it more and see if anyone knows a fix. I use Outlook 2013 on Windows 7 HP x64. But have seen this in other older versions of Outlook.

If I begin a new message, then during the writing of that message, I want to open an email in a folder, it often, but not always, dings at me and will not let me do this. Seems to happen more if the email contains a web link I put there by clicking SEND LINK AS EMAIL from my browser.

I have to exit the new email and save it as a draft before I can do that. Then go to my drafts and finish sending the email.

Any ideas?