It's still possible but most places with even a fraction of a brain implement rate limiting of all stripes and colors, so your odds are stacked against you if thats your tactic of choice. Of course there are still plenty of second rate and obscure services out there that can still be attacked by brute forcing logins.
At least brute forcing logins are mostly dead. Obviously the concept of bruteforcing is merely a tactic used to solve a wide range of problems, and many of them are still very relevant to security.
Since you were talking about email, I should point out you'd probably have a better time trying to figure out the password recovery security questions most email providers have, or just social engineer in some form the victim. Not even necessarily to get them to tell you their password, but getting them to click on some evil link of yours, run some evil executable of yours, or open some evil file for a commonly unpatched client software like adobe reader.
If you do really want to stick to brute forcing, youre going to want to at least establish that your tool or code can make a successful connection first. As 0E 800 hinted at, for a lot of forms that may mean solving some captcha, especially if the service later detects the automated behavior (as you can imagine, some places like google are more on the ball with this). Once you can get a successful login to a test account, then you need to find the lockout policies, usually its some rate policies such as no more than 3 attempts within a minute, or no more that 10 attempts in a single hour, or both. Dont assume those numbers though, merely an example on my part. Once you know the lockout rate you can throttle your tool better, cause slow is better than not at all. Depending on your target, it may be worthwhile to instead try a small amount of passwords and attempt them on a range of accounts instead of hammering one at a time. In lax windows networks(talking more like a company intranet here) this can be a nice tactic to avoid a lot of newbie account lockout settings set in Active Directory(of course if its a lax windows networks, there are a lot of more standard time tested methods that dont rely on brute forcing
)
Ultimately in my opinion, it takes far too much time and effort to get results brute forcing account info through some login form. If you're really committed you can eventually get some results but the way I see it its like trying to get inside a locked house. The front door doesnt budge so you decide to bash your forehead on the wall till you can make a hole to climb in, when instead you could have just opened a window.