Should I link to my primary domain in outbound sales and marketing emails? Can this impact my deliverability?
No, never. It is best to establish a vanity URL which is a fancy way to say but a domain with your primary domain in it but either with a different extension (.co, .io, etc), or another word in it (get, email, etc).
Then go into your domain registrar, and forward the vanity URL to the destination of your choosing. For example establish the vanity URL getinboxignite.com, and forward this to inboxignite.com. And in all of your outreaches, you would use getinboxingite.com instead of inboxignite.com. Go ahead and test it!
What domain and email should we use for outbound sales?