10 Tips to Improve Your Email Delivery
1. Ensure your "from" and "to" addresses are not the same. For example if the "from" says email@example.com and you send it to firstname.lastname@example.org it will most certainly be marked as spam.
2. Maintain a Good Text to Image Ratio. It is usually best to not include images at all; however, if you must include images, then take care not to send any image-only emails. Include text also. And optimize your images the best you can.
3. Don't sound like a Spammer! Don't use the word "free" too many times. Don't use ALL CAPS. Don't use lots of colored fonts. Only use one exclamation point at a time. Stay away from words you'd see in spam: Viagra, drugs, porn, guaranteed winner.
4. Be careful of inactive contacts. Contact engagement plays a big role in email delivery. By focusing on your active contacts you can increase your overall delivery.
5. Send using a consistent "from" email address. We do not suggest changing your "from" details often. Keeping it consistent can help build your reputation.
7. Avoid copying anything directly from Microsoft Word, Excel, PowerPoint, etc.. When you paste content directly from these applications additional characters will be automatically added.
8. Don't test using the same phrase as your subject and email contents. If you send an email with a very similar subject and message body it will likely be filtered as spam. (An example would be having the subject set to "this is a test" with the body set to "this is a test".)
9. Get Off Blacklists. If your email server is on a blacklist, it becomes extremely difficult to reliably send email, especially to new people on your lists.
10. Avoid Large Attachments and Certain Attachment Types. In general, .jpg, .gif, .png and .pdf attachments are safe to send, provided you include some content in the email as well. However, executable attachments such as .exe, .zip, .swf, etc. should be avoided entirely.
If you need to email a large attachment or an attachment type that usually can be flagged as spam or trigger virus scanners, we recommend a service such as DropBox.com. If the attachment contains sensitive data, you may consider using your company's secure FTP server.