Gmail uses filters and labels to help you manage your inbox. Some of these are automatically applied by Google, ie Social, Updates and Promotions, but you can also create your own. The labels appear in what looks like a regular folder list at the left of your Gmail screen, however labels are much more powerful than folders because any email you wish to keep can have two or more labels if desired.
By way of example, let's assume you are using Google G Suite and you have one or more alias email addresses attached to your main email address. We use this feature at LCC where any emails sent to firstname.lastname@example.org are received by email@example.com. From this example you will notice that there are a number of useful ways you can apply filters and labels to keep your inbox tidy.
In this scenario you have two email addresses as follows:
- firstname.lastname@example.org (email alias into the same mailbox)
So what you want to know is who has used which email address to get to you