You can create a list of the emails in a spreadsheet with each email in a different cell of the spreadsheet. When you want to email them, just open the spreadsheet and copy the entire row of email addresses. Then, go to your Gmail and paste them into the "To" field. This will put all the email addresses into your outgoing email without creating them as contacts.
Can Excel randomly select from a list?
Whether you're onboarding a new customer or keeping a user engaged, the sequence of your sends plays a crucial role in the success of each campaign. Consider how much information your target user needs, when he or she might need it, and why. Over on his blog, Jason Delodovici wrote a great post about a drip campaign that he spearheaded, noting the order he chose for each email—from signup to sale—and why.
How do I convert an email list to a CSV file?