Running Thunderbird 45.0 on two different Win 10 PCs. On one PC platform, that has not had Win 10 recently re-installed, one of 3 email account profiles is inaccessible for Account Setting changes such as Server, composition or font settings. When I select Account Settings The Wizard opens and It says, "An account already exists with this name, Please select another name. DOH?! WTF? The other two email profiles are fine. On a platform where Win 10 was freshly reinstalled, and Thunderbird 45.0 was reinstalled, I can't get the font sizes to display properly on the screen when editing, and the saved message clearly has two different font sizes even though, when pasted to a Word.exe document they appear to be the same size. I've messed with every font setting available in Options and Account Settings and neither of them gives me the result I expect; - a font size that is Arial 12 for EVERYTHING. Frankly, it doesn't help that there are two different places, 'Options' and 'Account Settings' to set the fonts. This is totally beyond me. Like you have to be a freakin' Java, JCL or some Unbuntu developer guru before you can use Thunderbird. When it was part of Netscape (gee, remember that one?) it was so simple to change the settings (of those that were available). Now Thunderbird is bloated beyond belief, and becoming way too difficult to use. Ya, I'm frustrated, can you tell? About now I want to punch Thunderbird in the throat!