Obviously, one should not open emails that come from a suspicious website, like 163. com. (apparently a popular Chinese scammer email origin thing). But can any cybersecurity issues arise from sending emails to a weird-ish email, not receiving?
Assuming you’re sending these emails naively using ordinary email apps like Outlook or Gmail, the only cybersecurity issue I can see is that you’ve told those folks that you exist. There’s nothing interesting they can glean from your email’s headers that aren’t already implied by your email address that you’ve helpfully given them.
Now what you put in the content of your email might have security implications. Such as including your bank account info, password, and PIN as they’ve requested you do. 
So don’t do that.
Thanks. I was just wondering if it was ever possible to get malware from sending an email, as opposed to receiving one. Can’t think of why, but you never know these days.
You can’t get malware from the act of sending an SMTP email. It’s a one-way, stateless, asynchronous transaction. It’s like sending a postcard in the mail. Someone else can intercept it, read it, tell where you sent it from and when, but they can’t reach through it and grab you.