After deleting the companyInfo.xml file from the domains folder, and reloading the domain, the main login screen no longer shows any custom HTML. So that's good. Still something odd going on, however.
Firstly, the companyInfo.xml file was re-created automatically shortly after it was deleted, with the following (I'm guessing default) contents:
<?xml version="1.0" encoding="utf-8"?>
<CompanyInfo>
<CustomInformation>
<HelpText />
<HelpLink />
<HelpLinkEnabled>False</HelpLinkEnabled>
<LoginText>Login to SmarterMail</LoginText>
<LoginTextEnabled>False</LoginTextEnabled>
</CustomInformation>
<LoginAreaConfig>
<enabled>False</enabled>
<LoginPageHtml><div id='companyinfo' style='max-width:420px;font-size:20px;'>
<br />
<center><img style='max-width:600px;max-height:140px;' src='http://smartertools.com/downloads/smartermail-logo.png' /></center>
<br />Hello, this is an example string of text. You can customize this text for your company.
<br /><br />For help please go to our <a href='http://example.com\' target='_blank'>support page</a>
<br /><br />
</div></LoginPageHtml>
<logoImage />
<loginBackgroundOption>DefaultImages</loginBackgroundOption>
<loginBackgroundImagePath />
<loginBackgroundColor />
</LoginAreaConfig>
</CompanyInfo>
No worries there.
But what is strange that when I login as the Sys Admin and go to Settings -> General Settings, just opening the page shows the "Save" button enabled. Clicking Save then changes the button to disabled (nothing was actually changed on the page). When I go to another page, and then back to the General Settings page, upon page load the "Save" button is enabled again.
Hope that helps,
Shaun