SendGrid is an email delivery service that increases email delivery rate. As per a generally accepted statistic, 20% of emails never make it to inbox. SendGrid improves the deliverability of emails so that more emails reach their intended recipients. You can use SendGrid directly with an email client, or you can use your existing email server, and configure it to route email via SendGrid.
Apart from that, SendGrid automatically provides advanced analytics related to your emails. At any time, you can see number of emails delivered, number bounced, email clicks, emails opened, spam reports, email unsubscribes, and more.
The great part of SendGrid is that it easily scales as per your requirements. If you are a starup, you probably send just a few emails per day, so you can start with free plan of SendGrid that lets you send/receive 200 emails daily. As you grow, you can move to paid accounts, that are quite fairly priced (basic account starts at around $10 per month with 10,000 emails per month credit).
If sending and receiving a major part of your business, then you might want to try SendGrid. Improving email delivery rate might be the simplest way to increase your revenue, without doing any additional marketing effort. Think over it. You can try SendGrid here. As I mentioned earlier, you can start with a free account that lets gives you 200 email credits per day.