Did you know you can customise the Office 365 login screen with your company branding?
Login to the Office 365 admin portal and select the Azure AD Managment portal.
Select your domain and then select the configure option to access the branding section.
You can also have your company workstations join the Azure domain so that users can login to their machines using their Office 365 credentials.
Let us know if you need assistance with customising your Office 365 environment.