Today's smart marketers want to engage their customers in new ways, and that means avoiding deliverability issues that stop your communication efforts dead in their tracks. Finding the right email service provider to help you improve deliverability and build long-term relationships with customers is forefront on many marketers' minds, but how can you differentiate one ESP from another? Here are five key questions to ask when comparing ESPs:

1) Do you support all authentication methods?
A lack of authentication subjects companies to increased scrutiny from anti-spam technologies. Look for an ESP that supports Sender Policy Framework, Sender ID, DomainKeys and DomainKeys Identified Mail.

2) How do you handle and report bounces?
All bounces are not created equal. You want an ESP that reacts to hard bounces and soft bounces differently and allows you to set parameters on how they're handled. For example, you may want to allow three delivery attempts for soft bounces over a certain period of time, but remove hard bounces from your list immediately.

3) Do you provide inbox monitoring?
Look for an ESP that can tell you if your message wound up in the recipient's inbox or went to their spam or bulk folder instead.

4) Do you give your clients a unique IP address?
Some ESPs will lump you in with other clients, making you vulnerable to their mistakes and putting your deliverability at risk through no fault of your own. Generally, choose an ESP that gives you your own IP address, which also has the benefit of allowing for quicker resolution if there's an ISP block.

5) How do you check for blacklisting?
You don't want to be the last one to know you're being blocked from communicating with your customers. Make sure your ESP casts a wide net when monitoring blacklists, including checking for blacklisted domains and URLs in addition to IP addresses.

For more tips on deliverability, visit our White Papers page to download the Silverpop white paper, "Email Delivery Rates Above 95%: 16 'Must Dos' to Make it Happen."