Gmail spams emails with words skype and outlook

Recently I noticed that a standard email that I send to people keeps getting marked consistently as spam on gmail while my other emails go through.

I tried to debug the issue and finally figured it out.

If I added the line: "My skype is : myEmail@outlook.com" , gmail would consistently mark it as spam with the message that this email looks like spam detected before by gmail. As soon as I removed that line, the same email would go through.

I couldn't believe this so I started making test accounts on gmail and this kept happening.

Have anyone else experienced this before ? If so this sounds like a very crappy practice from Google, is it legal ?