I use an email address with a single-letter username (m@...) and have never had a problem with services rejecting it. The only problem is that rarely when I sign up for a service using a random password like gAdlzIBVom4j3Paf, it tells me "your password cannot contain your username" because it contains the letter "m". Hah!

Good old security theatre

Haven't had that problem before, far more of a problem when I try to register with site specific email addresses like [email protected] which I've tried to get in the habit of doing.

Why do people use plus addresses when minus/hyphen addresses are much less problematic?

Are there many providers who support one, but not the other?

Some mail providers (eg Gmail) use the plus sign as a label. So your everything still gets routed to [email protected] but tagged "hn" or "twitter" or whatever.

It's quite a convenient way to have site specific addresses while still only having a single mailbox to manage.

I get told that my email is invalid by some apps, for using a .so domain. Apple was one that would not let me create an apple ID upon buying a new laptop. Eventually, I set up the machine without Apple ID, and opted to create it after the fact via apple.com which accepted it. It makes me wonder if it is intentionally a "Hard no" during system setup, and then a "well okay if you insist" when the user has installed the system without using an Apple ID as a last resort.

I have the same problem with my .one domain. Even though that TLD is about 7 years old, about 10% of sites won't accept it.

Yes, I did that single letter email way back around 2007-2008 and had it with my Bank (closed account for a company). Now, I can neither change nor login (not valid to them), and I have set a specific filter just to ignore that email from the Bank that keeps sending me newsletter and offers.

I don't use the short oin.am as my primary (which is oinam.com), I have it as a alias domain, allowing me to quickly say/hand-write my email to someone and continue the conversation from my main domain -- say, ß@oin.am.

I literally had a bank tell me my email was invalid today. It was 2 letters before the @, and I think that's why. I'll probably come up with a longer one that I like (I own the domain) later and try again, but it just felt incredibly lame for them to reject my email like that.

Yep, I’ve encountered that problem fairly often. These days, I only use that email for vanity.

Hah I had the email address [email protected] for a little while - same thing, everyone just got confused by it.