Access owa login

https://mail.1ask2.com/owa

View Source Code and find the location of lgntopl.gif and lgntopr.gif, e.g.

src="/owa/14.1.270.1/themes/resources/lgntopl.gif" 
src="/owa/14.1.270.1/themes/resources/lgntopr.gif" 


rename them as lgntopl_bak.gif and lgntopr_bak.gif

create your own images named them as lgntopl.gif and lgntopr.gif and put them to 
C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Owa\14.1.270.1\themes\resources

restart IIS

Customize the logon screen with additional text

Create a html format instruction, e.g. instruction.html, and save it to folder:

C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Owa\auth

Modify the logon.aspx file

<table class="mid tblConn">
<!-- #include file="instruction.html" -->