If you mean an email (or the part before the @), also no. People sometimes sign up from addresses like [email protected], and "dear contact" would be super confusing.
The "right thing to do" is to have a "what should we call you" field, which should be completely separate from any names collected for legal purposes, if any.
I was going for the principle that we're not trying to mimic human emotions when it's a mail to remind you to accept the latest TOS.
So, no "Dear", no trying to come up with something socially acceptable, just plain "[email protected], please review our newest Terms and Services at https://....../...."
The "what should we call you" field sounds attractive, but would be ripe for abuse IMHO. Not on technical terms, but users would definitely play with it to have you send "Mrs DeepshitFuckHorse please confirm your email at...." to random addresses for instance, or any other vector that we're not thinking about right now.
I've started to prefer messages that just start with "Hello,".
I tend to use fuck/off as name/surname for completely throwaway accounts, and "dear mr. Fuck" is something I received once.
There are several people I know primarily through wechat, where it's almost always unnecessary to address people by name because messages have only one recipient. Sometimes this has led to conversations like this:
> What should I call you? 颖?
> OK.
[I was not especially reassured by that response.]
Heh, there are still some people who call me by my nickname back from 2000s. It doesn't help what it means something between "the beast" and "the thing" and I had people of the old clout be quite offended by it. Including my mother.
You got off light. I had a good number of people call me by my username at my undergrad.
When I went to grad school, they let us select user ids. My user name matched my first name, most elegant solution to that problem yet ;)
Handling people's name is I think the bane of our field, and leads to many of the awful choices like forcing fields with a first and last name for instance, or requesting people's gender to properly set the Mr and Mrs. As a dev I'm not happy about it, as a user I hate it, I'm not sure the majority of people are happy either with the current state of things.
Accepting that it's a machine sending the mail could simplify all of this quite a bit, provided people are fine by being addressed in an impersonal and inorganic way.