Hello @UPC-Communications ,
Here are some general best practices for delivery.
Delivery can have a lot of variables, from elements on our side, on your side, on the recipient's side, and in their email system company's side. It's a best practive to setup self-authentication within your account, if you have your own domain.
If you'd like to learn more about safelisting, and what it entails:
Safelisting domains in a security system
Safelisting email addresses in an email client or security system
If you're wanting more in-depth, specialized insight on your current deliverability, it'd be worth speaking with one of our Delivery agents.
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