One of the keys to good phishing is how the mail is delivered. In the past I used services such as Sendgrid or Rackspace for mail hosting and delivery. What you may find over time is that sometimes the domains you want to use trigger automated alerts and lock down your account at certain service providers. Bam, there goes your delivery method. You have backup mail delivery options if you can’t convince customer service why you didn’t violate their terms of service, right?
One of my backup mail delivery options I eventually turned into my primary was self-hosting my own mail servers. Initially I tried Postfix and some other options, but man that was a pain to get going. I already have enough complexity in my life. Then I found an all in one mail server and it is dockerized. You can spin that thing up with a couple commands and have gmail like webmail, a web interface to add domains and mail boxes and quickly create DKIM keys. Everything you need in a phishing email SMTP solution. It is called Mailcow. Check it out if you are considering self-hosting an email server for phishing and it will make your life a whole lot easier. It runs decently well on a 2GB RAM instance at Vultr. I found less than that it really doesn’t work well at all.