Whatever Mail server client you have (desktop, mobile or other)
If your 'Mail' delivers a legitimate message to junk, you can do THREE things.
Teach your Mail's filter to allow future messages. Open the junk folder and find the message. Move the message into the inbox and then
Add our email to the address book. Open the message, right-click the sender email address, and choose Add to Contacts
At the bottom of each email transmission we send you, you can choose to 'click' where it says, "Whitelist this domain by adding us to your address book here."
Simple. Done. Carry On.