Looking for some advice or direction to a tool that I cannot find through a Google search.
Long story short I am doing some investigation for a private client whose had their bank account compromised and a substantial amount of money (for them especially) e-transferred to a Gmail account they don't recognize. I have spent the better part of the last two hours trying various Google searches and methods of extracting the owner of the account and been so far unsuccessful.
I have tried:

- Web based tools such as beenverified and peoplesearch

- The "calendar" and "hover" methods on Gmail

- Social media searches

- Reverse whois lookups

So far none of these have been successful and I am looking for any advice or help to extract a username or location from this Gmail address. They have to have provided something to sign up for it and I am hoping that even if it is a fake or one-off account that these details might have clues that will lead me to the next step.
Any help or advice is appreciated

I want to find all my old Gmail accounts that I've forgotten about, is there a way to search for email addresses by the registered name?

I have an account I used to use, and forgot it. One thing, though, is that I have the specific numbers that were at the end of the email address. Now, it wasn’t a simple year number, it is very specific numbers, as stated before. A lot of them, which made me wonder if I’ll be able to somehow search for it, as I’m guessing most email addresses don’t have those numbers.

if I were to search it up, I believe I would recognize the username, as I remember it had 2 initials in the start, but do not recall what they were. So, two questions, I suppose:

Firstly, is there some way to search email addresses— and I’m on mobile, where gmail no longer supports desktop version— with some kind of software or in gmail itself?

And, lets say, if I were able to, would only the numbers at the end of it work?