How do I remove [SPAM] designation when message is legitimate?

[gaorsk]

Occasionally, an incoming message has had [SPAM] inserted as the first word
on the subject line. How do I let the system know when it is legitimate and
not spam?

 

[F. H. Muffman]

Occasionally, an incoming message has had [SPAM] inserted as the first
word
on the subject line. How do I let the system know when it is legitimate
and
not spam?

Disable whatever add-in is adding it. Outlook does not do tihs without
external assistance.