There is a post that incorrectly answers this question. The post says "Open Account Settings. Outgoing Server/SMTP is at the very bottom of the left pane where all accounts are listed. There is a button to edit an existing SMTP server. " It is NOT a button and it is NOT at the bottom, it is a menu item, appearing right under "Local folders", at least in my 38.6 version. At least the post did lead me in the right direction. I only found this accidentally after unsuccessfully trying to find an item on the "Actions" button at the bottom. See the image.