Nodemailer works on local PC, but not on server

I want to send emails via Gmail (OAuth) from a node.js application with nodemailer. It works perfectly fine on my PC, but if I try it from my Linode server nothing happens. I don't get an error, it just times out after a few minutes. Firewall is disabled and because the code works on my local machine, I don't know where to start. Maybe someone knows where to start and help me with this issue.
Thanks a lot