Anything that may trigger an additional
spam filter or that your prospects may read as spam should be avoided.
No spam words such as free trial, special characters or text formatting. For both spam filters and people, these are indicators of spam or malware.
Additionally, avoid the use of images, attachments, or hyperlinks anywhere in the text.
It may be tempting to send out white papers or sign up links, but when you’re running numerous campaigns, it ends up being more detrimental to your deliverability than anything else. Only start sending additional content once you’ve ensured their responsiveness and interest. Anything before that will be seen negatively.
Signatures should also be as clean as possible, so that your prospects are more likely to receive the email in their inbox.
A good way to do this is to create a separate address purely for sending out emails. Keep your official signature and email for internal issues or existing clients separate from the email you use to send out campaigns.