It takes about 5 minutes to setup and does not back date so worth doing ASAP to start and continue gathering YOUR data
which is free and provides insight into these gmail (and gsuite):
These are the steps to set it up: 
(It only takes about 5 minutes to setup)
  1. Go to postmaster.google.com.
  2. On the bottom-right, click the + button.
  3. In the box that pops up, enter your authentication domain.
  4. Next, prove that you own the domain by adding a DNS TXT or a DNS CNAME record.

Notes:

  • Each account needs a separate DNS verification record, and you won’t be able to see your traffic analytics until you complete this step (although you can skip the step and add this later).
The individual dashboards:
Spam rate:
This dashboard shows the volume of user-report spam vs. email that was sent to the inbox. Only emails authenticated by DKIM are eligible for spam rate calculation.
 
Domain & IP Reputation:
Domain and IP reputation gives a sense of whether the Gmail spam filter might mark emails from that Domain or IP as spam or not. Keep in mind that spam filtering is based on thousands of signals, and that Domain & IP reputation are just two of them.
 
Feedback Loop:

This dashboard only shows up for senders who’ve implemented the Gmail Spam Feedback Loop (FBL). Click any data point on the graph to see a table with the identifiers flagged by FBL and their corresponding spam rates.

 
Authentication

Shows traffic that passed SPF, DKIM & DMARC, over all received traffic that attempted authentication.

  • SPF Graph — Shows percentage of mail that passed SPF vs all mail from that domain, that attempted spf (ie. excludes any spoofed mail).
  • DKIM Graph — Shows percentage of mail that passed DKIM vs all mail from that domain, that attempted DKIM (ie. excludes any spoofed mail).
  • DMARC Graph — Shows percentage of mail that passed DMARC alignment vs all mail received from the domain, that passed either of SPF or DKIM.
 
Encryption:
Shows TLS encrypted traffic vs. all mail received from that domain, and consists of two distinct graphs within the same dashboard.
 
Delivery Errors
Shows rejected/temp-failed traffic vs all authenticated traffic coming from that domain, within a single graph. Typically messages are rejected or temp-failed with the SMTP error codes 550 or 421 respectively. Click a data point to see a table with the reason behind why the traffic was rejected or temp-failed.