I like Gmail, but sometimes I have to use the email under the different domain and I do not want to integrate my domain with google ecosystem (G-Suite). I tried to use SMTP + POP3 integration but after some DDoS attacks to smaller mail servers some of Google IPs were blacklisted and I was unable to use this integration more. So I found another way how to fix this.

-1. Create Gmail of you do not have one

I assume you are familiar with Gmail and already have one account there 🙂

0. Register your domain and create mailbox

Use your favourite domain “seller” and create a mailbox there (e.g.: [email protected])

1. Forward all emails to your Gmail

Setup mail forwarding for your custom domain to your Gmail mailbox
e.g.: [email protected] -> [email protected]
This will substitute POP3 connection

2. Let Gmail send emails through your custom domain

This is the most difficult part because we have to do multiple steps:

• 1. Check if you have Less secure app access enabled via this link
  • 1.1 If not (when you have 2FA enabled) create app-password using this link
• 2. In Gmail go to Settings / Accounts and Import / Send mail as / Add another email address
  • On the first tab add custom name and under Email address put your custom domain ([email protected]) and keep Treat as an alias ticked.
  • On the second tab add:
    • SMTP Server: smtp.gmail.com
    • Port: 465 or 587
    • Username: Name of your Gmail account (my gmail is filip@gmail.com so I put filip, if I had test-mail@gmail.com I will up test-mail)
    • Password: Your Gmail password (if you have Less secure app access enabled) or Password generated through step 1.1
    • Use TLS

3. Setup SPF record

Go back to your domain provider and edit DNS configuration by adding one more record – TXT

• Host: @
• Value: v=spf1 include:_spf.google.com ~all
• TTL: 3600 or Default

Links:
https://support.google.com/a/answer/33786?hl=en