First, let's make one thing clear. This isn't your average guide on how to improve email deliverability that will tell you always use double opt-in blah blah blah. Since my customers usually don't have double opt-in lists we’ll focus on other ways to improve email deliverability. But of course, we must touch some the well-known ones as well. The boring This are all the ones you should already know that includes but are not limited to: Subject lines should be related but catch readers attention Use a subdomain for all sending activities Don’t send to hard bounced contacts twice Remove soft bounces after 3 - 4 bounces Make sure you use SPF and DKIM Avoid spam traps Use feedback loops (FBL) Don’t over mail Don’t add attachments Keep your email size small Use spam checker before you send Make unsubscribing easy and instant ... The part they don't tell you Ok, this is where things get interesting and a lot more technical. Please for th...