How to add a button to a pre-existing tab on ribbon (C#)?

Question

I\'ve successfully created a new tab and put it next to the pre-existing ones. Then I realized that I\'ll only have one button on it, so it makes more sense (for now) to put it

Answer 1

The attribute idMso is correct, but the id for the tab you want is TabMail. You can find a packed set of Excel-files containing lists of Office 2010 control IDs on MSDN. Then, as mentioned in a comment to the question, your sample XML may be missing the customUI and ribbon-tags. (Disclaimer: I haven't customized the ribbon in Outlook, only Word, Excel and PowerPoint, but I would guess they work the same?)

Try something like the this: