From the limited info you've provided it sounds more like your email account has been compromised rather than your machine. There are very few trojans for Mac and I don't believe any of them mess with your email. The other issues you're noticing likely are just coincidence. As suggested above, change your password for your email account and be sure to use a strong password e.g., at least 8 characters, use letters, numbers, and special character if allowed on account, and nothing you can find in a dictionary.