All too often marketers find their emails ending up in the junk folder. There are lots of reasons that this can happen but a common cause is the content of the email.
All ISPs use content filters to remove and block emails that contain certain known spam words, things like viagra, software, replica watches. Due to the sheer number of spam emails that are sent every single day, some good emails get caught.
1) Avoid shouting in the subject line - OPEN NOW TO FIND OUT MORE - make sure your subject line isn't all in captials.
2) Image to text ratio - ideally 60% text to 40% images. Remember a lot of ISP turn images off by default. Make sure your important message/call to action is not an image, it's likely to get missed.
3) Send a text version - It's very tempting to just send HTML emails, but sending a plain text message is good practice.
4) Have a recognisable and contant 'From' name - avoid using the name of your website in the From part of your emails.
5) Don't use !!!! and .... in the subject line and body copy