@neonfour is right, though I wanted to add some details.
A firewall would only be able to do anything if you hosted the email server yourself at your house. You don't do this. Your phone just connects to an email server somewhere online and downloads your emails.
What you need to do is setup email filtering with your email provider, not within the samsung email app. Look for a trend with the spam, set a filter to block any mail with that trend in it. That's the most basic way to handle this.
Also kinda side thing, firewalls are sorta useless for normal home users, they don't serve any purpose. (That's not exactly true but hang on with me). They used to block outside connections talking to your devices. But in current years, your router handles that for you with NAT.
All a modern consumer firewall does now is allow you to block certain programs from using the internet.
On untrusted wifi not at your home, they are set to block basically everything from the outside coming in, but that's not going to be needed in a normal home. Oh and that's to block other people on the wifi talking to your pc, not the internet from talking to your pc
