To change the appearance of outgoing emails in BlueMail, please tap the gray rectangle with an arrow icon located just below and to the right of the Subject line.

You can tap the arrow icon again to hide this toolbar.

BlueMail_Google_Play_Rich_Text

In addition to B and U, the additional icons perform the following functions:

BlueMail_Rich_Text_Bar Bold
Italic
Underline
Increase Text Size
Change Fonts
Change Text Color
Insert Image
Add Hyperlink