How to add a Gmail/Gsuite account through Custom Inbox option

Adding a Gmail or Gsuite account can be done through the custom email inbox option.

First, some settings in Gmail will need to be changed in order to allow Quickmail access to the inbox and to send emails. 

Go to the Gmail account's settings and enable IMAP access (needed for reply detection):



After that, go to this page -> https://myaccount.google.com/lesssecureapps
and allow less secure apps access to the account (this is needed to send emails out): 



Once those are done, the Gmail/Gsuite email account can be added.  
But instead of clicking the "Add your Gmail Account now", use the "Add a Custom Inbox" option. 

Use the following credentials in the custom inbox fields: 

Email: [Your Gmail/Gsuite email address]

SMTP:  

Server address: smtp.gmail.com
Server Port: 587 
User Login: [Your Gmail/Gsuite email address] 
Password: [Your Gmail/Gsuite email password]

IMAP:  

Server address: imap.gmail.com
Server Port: 993
User Login: [Your Gmail/Gsuite email address]
Password: [Your Gmail/Gsuite email password]

After adding the custom inbox, go to https://www.google.com/accounts/DisplayUnlockCaptcha
and allow access by clicking "Continue".

- This is to confirm access to the Gmail/GSuite account. 

Finally, tests can be made to confirm that the email account has been successfully linked. 
Here's how to send test emails - Sending Test Emails