I was absolutely shocked to learn this is how Gmail works.
— Jack Yan 甄爵恩 (@jackyan) September 27, 2020
PS.: This was the image linked above, before I locked my account:
As you’ll read in the thread, this has been confirmed by other Gmail users.
That should rule out ever using Gmail for secure communications. Not that you should be using a service like that for anything important, but the fact is Gmail has become ubiquitous, and I believe a lot of people don’t know any better.
Just imagine being able to receive some emails meant for your rival by signing up to an address that varies from it by a full stop or period.
Secondly, we’ve noticed a large amount of spam where we can trace (via Spamcop) the origins back to Gmail. Oftentimes they have Gmail reply addresses, as in the case of 419 scams (where they may use another ISP or email service with a “sacrificial” address to send them). Why would you risk being among that lot?
Add this to the massive list of shortcomings already detailed here and elsewhere and you have a totally unreliable platform that doesn’t really give a toss. They didn’t care when they removed my friend’s blog in 2009 and then obstructed any attempt to get it back, until a product manager became involved. They didn’t care when their website blacklisting service libelled clean sites in 2013, telling people not to visit them or link to them. And they don’t care now.
There really is no reason to use Gmail. You’ll risk your emails going to someone else with a similar address, and you’ll be among the company of unethical actors. I can truly say that if Gmail weren’t this ubiquitous, and used by so many friends, I’d just set up a rule on our server and block the lot.