I have my yahoo email account on my Samsung Galaxy S5

[AC Question]

but I want to know how to block spam

 

[Crashdamage]

I don't use Yahoo but it"s pretty much the same for all the major email services. Log into your email account online, using the webmail interface, and enable spam filtering there. Yahoo probably also has the ability in create custom spam filters for specific offenders.

Android since v1.0. Linux user since 2001.