It is still effective if you have a quality email list. Let send newsletter or promotions to your list and make sure that your subscribers want to buy or concern about what you offered in your email then
As Marc says, you need a good email list otherwise it doesn't work too well. Email marketing can use different approaches. I tried sending cold emails for a long time but found for the most part it was just a total waste of time.
Before start doing anything with your LinkedIn or email or anything, please make sure that you know who is your buyer persona or the ideal customer profile. Otherwise, all your further efforts would be converted to spam.
Also, don’t forget to optimize your LinkedIn Profile before you start your outbound campaign.
Before sending an email research your audience and make a proper database. You may know well about your audience(Your target audience may be from linkedIn, Facebook, Twitter, or Instagram) get an email from extension from all social media Then you will send an email.