It’s almost certainly fine. Emails are not shared to other instances.
However, when you go around the internet giving your email address to random sites, eventually you’re gonna hit the wrong site and at the very least end up with a bunch of spam or having your email sold to advertisers. It’s a good idea to use an email privacy service - basically when you sign up for things like newsletters or random sites you generate a new random email, then if anyone emails that email it gets forwarded to your actual email address. Some of the services even let you reply to the email and they make it look like you relied from the alias.
We’re on different instances and links can be funny at the moment so I’ll copy a recent post I did:
You don’t need to provide an email address to sign up at most of the big instances. I think lemmy.world is the exception. Even your instance lemmy.ca does not require an email address.
If you really want to provide one, you could use a service that does email forwarding. Some examples are simplelogin.io (owned by Proton Mail), and Firefox Relay (Owned by Mozilla, makers of the Firefox browser). These both have free tiers. There is also duckduckgo.com/email/ from the people who make the privacy focused search engine DuckDuckGo. That one I believe gives you unlimited new randomised email addresses for free. Very low attachment size limit but great for something like Lemmy.
You install an extension in your browser then you can generate emails whenever you need.
Personally I pay for Firefox Relay, which has a small free tier (I think 5 emails) but the paid version is $10 for a year which I think is worth it.