Just email marketing don’t do it anymore.
The modern world of inbound marketing has changed a lot over the years and is still changing every day. We need to be doing a lot more than just email marketing. As a business if you are still just dependant on email only, you are bound to hit a few barriers.
Here are some of the hurdles or challenges you may have to deal with, that is, if you want to hit your target audience with email only.

Email marketing takes time.

Pure ESP or email service provider hardly ever has any scope to fine tune or re-target your campaigns. This means you will end up doing a lot of the targeting work manually to ensure you are sending the right message (email) to the right recipient (audience).
But with automation, you can cut out the time consuming manual work and focus on creating automated reaction based campaigns that can help you nurture and score your leads. The time you save can be invested in focusing on your core business.

Sending hot leads to you or your sales team
Just sending emails may get responses but it won’t get you hot leads that are ready to convert in to a paying customer. With email blasts, only thing that you are tracking are open rates and click through rates. Even if you create a list for everyone who has clicked on a link to go check out your website, that still is not a purchase ready customer. If you have their numbers, you must call ALL of them up to find out who is genuinely interested in your product or services and who is just curious.
There is no bigger waste for a sales rep to waste time calling up cold leads that probably will never convert. This is also not good for team morale.

With marketing automation, you can nurture your leads and segment them as according their level of interest in your services. You can also score them by demographics and the actions they have taken. Then only when you are sure that the lead is ready to buy, send them to your sales team to close them.

Spamming is not engaging.
Let’s say that hypothetically you have a large list (leads). It is tempting to send a few email blasts to see if you get any interests. But the problem is you still won’t have any about where they are in your sales cycle or even if your content is resonating with them or not. Given how long it takes to set up a single email blast, it is nearly impossible to be strategic at a granular level.
However, with marketing automation you can use various lead nurturing methods to score your audience and segment them. This helps you to send relevant campaigns that has a higher chance to engage them to your brand and your message. Automated campaigns are always an easier method to keep your audience engaged.

Scaling trouble!!!
As your company grows, it is impossible to keep your audience engaged with just email marketing. The more leads you have, more time it will take you to create individual ad hoc email campaigns for them. More leads means more hassle and more time investment.
On the other hand, it is incredibly easy to scale with marketing automation as all you need to do is create the funnels and keep adding more leads on the top of it. Every now and then just adjust and enhance the nurturing process. That’s all you need. Automation means more action with minimal time investment.

What’s the bottom line.
The big cash question. It is tediously difficult to attribute revenue on email blasts. You never know what triggered a recipient to convert and what effort on your part pushed them to the sale. It is also difficult to replicate that effort to get more sales as email marketing treats all your customers as same.

Marketing automation comes with built in functionality to measure all efforts at a granular level and tells you exactly what is working and what is not. It syncs up with existing CRM and tells you what is the exact cost of an individual lead and hence spells out a easy to understand “cost of sales”.