Emails went to spam for no apparent reason

%3CLINGO-SUB%20id%3D%22lingo-sub-1131616%22%20slang%3D%22en-US%22%3EMessages%20went%20to%20spam%20for%20apparent%20reason%3C%2FLINGO-SUB%3E%3CLINGO-BODY%20id%3D%22lingo-body-1131616%22%20slang%3D%22en-US%22%3E%3CP%3ESome%20messages%20from%20a%20certain%20gmail%20address%20are%20being%20routed%20to%20spam.%3C%2FP%3E%3CP%3EThe%20message%20itself%20seems%20legit.%3C%2FP%3E%3CP%3EWhat%20could%20be%20the%20reason%3F%3C%2FP%3E%3CP%3E%26nbsp%3B%3C%2FP%3E%3CP%3EThanks%3C%2FP%3E%3C%2FLINGO-BODY%3E%3CLINGO-LABS%20id%3D%22lingo-labs-1131616%22%20slang%3D%22en-US%22%3E%3CLINGO-LABEL%3EOffice%20365%3C%2FLINGO-LABEL%3E%3C%2FLINGO-LABS%3E
Highlighted
Visitor

Some emails from a certain gmail address are being routed to spam.

The message itself seems legit.

What could be the reason?

 

Thanks