While using an email template, it may work properly in Outlook but not in Gmail, This issue may due to the Internal Usage of CSS( By using a <style> element in the <head> section), To avoid the issue try to use styling in Inline CSS (By using the style attribute inside HTML elements).
Tips:
- Use inline CSS only
- Use Tables for layout
- For more information about Email templates ,
refer :https://code.tutsplus.com/tutorials/getting-started-with-html-emails–net-17200