Below are Email Deliverability tips and tricks from leading industry experts. While none of these are required, they all come highly recommend from SendGrid.

First and foremost, ask yourself this question: Am I sending the right message to the right person at the right time with the right frequency? Overall Email Deliverability is influenced by how your recipients interact with your messages. If your messages are opened in a timely manner, images are displayed, and links are clicked, then mail providers trust you as a valid sender. If messages pile-up, remain unopened, or get marked as Spam, mail providers won't be as comfortable placing your messages in the inbox.

The second biggest factor in inbox delivery is content. It's very important to ensure your emails meet all CAN-SPAM requirements:

http://business.ftc.gov/documents/bus61-can-spam-act-compliance-guide-business

Next, all email providers look for Unsubscribe links in all emails. Even though it may not make sense for transactional mail, it can make the difference in messages arriving in the inbox or the Spam folder. Our Subscription Tracking App automatically inserts an Unsubscribe link into all your mails and maintains the Unsubscribe list. The Subscription Tracking application is available for all Bronze level accounts and higher.

Maximum company visibility helps as well. Placing your company name in the Subject line of your emails and including your physical mailing address and phone number in your email footers helps mail providers recognize you as a legitimate company and sender of email.

Our Click Tracking application can sometimes trip up Spam Filters. If you have Click Tracking enabled, we'll replace any links within HTML <a> tags with unique links that redirect through our service. As such if you use the original link as the clickable link text in your <a> tag, when the Click Tracking link is replaced it creates irregularity between where the link appears to go and where it actually goes. For example the original link:

<a href="http://www.sendgrid.com">http://www.sendgrid.com</a>

gets replaced with a much longer Click Tracked link:

<a href="http://beertemp.sendgrid.net/wf/click?upn=a2quqXSHnxzJyDEtVGmF4w3cW...>

This is very similar to Phishing emails and as such may cause messages to go to the Spam Folder rather than the inbox. To get around this, use something descriptive for the link text rather than the link itself in your mesages:

<a href="http://www.sendgrid.com">Click to visit SendGrid</a>

You should also consider how you include images and attachments in your messages. As it is impossible to know how a receiving server treats attachments, we recommend using the HTML <img> tag to include images in your messages and we also recommend linking to files rather than including them as attachments. Images must be hosted on your own or on a public facing server to be included via the HTML <img> tag. Secure site logins or credentials can be used to track who is coming to your site to download files. This helps ensure that your message gets to the recipient regardless of any attachment restrictions on the receiving mail server.

Finally, there are external services you can use to get an idea of how mail providers analyze your emails:

http://isnotspam.com/ AND http://www.mail-tester.com/

You send emails to a capture address at one of these services and they reply with a breakdown of all the positive and negative factors of your emails. This helps you isolate and fix specific issues that may be sending your email to the Spam folder rather than the inbox.

SendGrid has also released the article Everything You Need To Know About Email Delivery highlighting these and more deliverability tips. Our Compliance team also has a set of Recommended Sending Practices & Methods covering industry standards such as confirmation and invitation emails.