Gmail is now the most popular mailbox provider on the planet, and to that end they keep their technology very close to the vest by running a self sustained system that does not partner with any other entities or utilize some of the common tools like whitelisting and feedback loops adopted by other ISPs. As a result, it’s sometimes difficult for senders to troubleshoot and navigate through Gmail delivery failures. However, they do provide some guidance to help prevent your messages from being marked as spam. Here are five tactics you can use to ensure delivery at Gmail. Get added to user contact lists. Gmail advises that you ask users to add your ‘From’ address to their Contacts list. This will tell Gmail they are expecting and want email from your organization. If your email does end up in the spam folder, users can proactively click ‘Not Spam’ to tell Gmail that your email is legitimate. Use different IPs and/or domains. If sending marketing and transactional email, separate these two email streams on different IPs or send from different domains. Authenticate your mail. Help Gmail identify you. Publish an SPF record or sign your mail with DKIM or DomainKeys. This will help Gmail identify your email streams from others pretending to be from your brand. Be consistent by authenticating all of the mail streams that are sent from your domain. Otherwise, your messages might not get delivered. Unsubscribe users promptly when requested. Make sure an unsubscribe link is prominently displayed in each email you send. Gmail also suggests that you include a ‘List-Unsubscribe’ header which points to an email address the user can use to unsubscribe from future mailings. Additionally, unsubscribe email addresses that bounce multiple times to avoid your emails being marked as spam. Watch your engagement levels. Gmail uses engagement to help determine delivery. This is also the impetus behind Gmail’s Priority Inbox which measures the interaction rates between the sender and the recipient. Therefore, run a reengagement program to users who have not opened or clicked on your emails in 60 days, and continue to focus on optimizing your program for maximum response. While Gmail remains elusive in many ways, they do follow much of the same protocol as the other ISPs. Therefore, following standard email best practices will help your email delivery at Gmail. To get more details on Gmail’s recommendations, check out their Bulk Senders Guide. You can also download our email deliverability guide to learn everything you need to know about delivery through your web application.