Hello @AndreG40 ,
Sounds like the client or security program for you is questioning the source of the from address. One thing that can be done is to safelist the from address that you are sending out messages from in your inbox. Below I have provided two links to knowledge base articles for us that cover adding emails to safe sender list and if need be, safe listing within security program.
Safelist email addresses in an email client or security program
Safelist Constant Contact web domains in a security program
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