Blocked port 25 is a false or real problem?

Hi,

I need to know if a blocked port 25 is a false or real problem.

I have a VPS on Google GCE.

But, Google blocks port 25, I believe both incoming and outgoing connections (but please correct me if I'm wrong)

There is an option on WHM to use an alternate port (like 26, for example).

My question is:
- if I set up a VPS on Google, with WHM and cPanel, and use port 26 instead of 25, will everything work fine with my cPanel accounts (sending and receiving emails)?
- or will I have some problems? If so, what kind of problems?

Note:
I know I could use Mailgun, Sendgrid and Mailjet as a relay host, but I prefer not to do that, in this VPS.

 

Thank you for your answer.

But, that means that every VPS on Google GCE is using a smart host to send emails?

 

Thank you for both your answers.
I know Sendgrid, Mailgun and Mailjet, and I've used their services for sending newsletters and I've also set up servers using them as a smart host.
They work fine and easy to work with. They really are and impressed me. They do a fine job.
But, that's not the point. The point is that sometimes you just need a server to send emails directly without using a smart host. And I thought there was a way of doing that in Google GCE. I guess I have to use another ISP in this cases.