If you are running wordpress in your vps or dedicated and if you are newbie to linux it will be hard to fix if something goes wrong.
Also if your server is sending thousands of emails per day with wordpress and got blacklisted on gmail,yahoo accounts it will be real pain. And you will need to move to new ip or work to get new ip assigned to your server.
But there is a nice way of fixing things if you got php send mail function not working or ip blacklist problems. Actually I recommend this even you didn’t got such problems because risk of getting blacklisted will be solved by doing this!
Ok whats the solution?
Its simple there is a wordpress plugin called “WP Mail SMTP” and you can use it to easily configure wordpress to use external email provider who support SMTP functions like gmail,google apps to send your wordpress emails such as new comment notifications.