Hi everybody,
I figured out the problem and am now able to email support@meraki.com just fine. It was specifically caused by how Google Drive and Google Workspace handle interactions with external users. It's likely not something Meraki could fix unless they can see my account as some sort of guest in their own Workspace. I don't know much about how that works since we don't use Google for our email provider.
I imagine this is a very niche problem, but I'll add what I found out and my best assumptions below.
Q1: Why did the bounce-back say my Gmail account was disabled?
A: Early last year, I received a Google Drive document from a vendor using a Google environment. I never created an account to access the document but I did receive a One-Time-Passcode to open the file inside of Google Drive. Near as I can tell, me accessing that document auto-created a Google account using my work email even though I didn't go through any setup process. I have not accessed that file since the day I received it, thus I have not even opened Google Drive for probably over a year. I imagine Google auto-suspends accounts like these after a period of no usage.
Q2: Why did the bounce-back happen when sending to Meraki support's email address but not others?
A: Google processes emails to Workspace Group accounts and individual accounts differently. If a Gmail account is disabled (my auto-created account), it cannot send to group accounts. My assumption is support@meraki.com is one of those Workspace Group accounts. My organization deals with individuals so this is probably the first time anyone here has sent an email to a Google Group account.
Q3: How did it get fixed?
A: I had to log in to the Google account tied to my organization email. That's it. Before I even logged in, it said my account was disabled. I was then emailed a One-Time-Passcode to sign in and it forced me to create a password and setup a Google account. The account I created doesn't appear to be set up like a typical account. It does not have Gmail capabilities by default, certain settings are turned off, etc.
Overall, this was an easy fix once I realized what happened. I now know more about Google Workspace environments than I ever wished. Google auto-creating an account like that then suspending it is a bit frustrating though. Especially when the person doesn't realize their Microsoft work email even has a Google account!
Thanks to everybody who gave suggestions!