Needs checking: real brands rarely do it, scammers imitate it
A brand writing from Gmail, Outlook or Yahoo: check first
A sender's address at a free mailbox is one of the signs creators share most. A brand has a domain name; scammers have a free mailbox.
What it looks like
Clara, partnerships at Glow Example, clara.glow.example@gmail.com
Why it is a sign
Anyone can create a "brand.partnerships@gmail.com" address in two minutes. An address in its own name is the first thing a brand owns and the first thing a scammer does not have.
What a real brand does
A real brand writes from its domain (firstname@brand.com). An agency writes from its own, and says which brand it is for. A very small brand may still use a free mailbox: hence "needs checking", not "scam".
What to do
Look for the person on the brand's website or a professional network. Answer asking for an address in the brand's name, or write to the brand through its website to confirm.