I create a filter for someone's email and it automatically goes to a folder. For all of his following emails, they go into that folder. But for anyone who REPLIES to His email it goes directly in my inbox. Is there a setting in Gmail that will filter these replies (follow-up) emails into the same folder as the sender's?
It seems you have a filter like this:
from:firstname.lastname@example.org apply label: jdoe_messages
The simplest way to have messages from John Doe, as well as message sent to him, is:
has the words: (from:email@example.com OR to:firstname.lastname@example.org) apply label jdoe_messages
That way, any message from John Doe, or with John Doe's email address in the
to: field, will be seen by the same filter.