A PowerShell based typosquatting tool based on the work of O365Squad here: https://github.com/O365Squad/O365-Squatting.
New-TypoSquatDomain -Domainname google.com
Creates a list of alternative domains using multiple techniques.
Get-O365TypoSquats -Domainname typosqauteddomain.com
checks if typosqauteddomain.sharepoint.com, typosqauteddomain.onmicrosoft.com and typosqauteddomain.com exists, returns true or false for each property.
More documentation, adding automatic spamfiltering.