Find the questions new customers ask
Pull the tickets from customers in their first month and tag the topics. The three or four that come up most are your email topics. This keeps the sequence about what people need, not what you want to announce.
Send fewer, shorter emails
Three or four emails over the first two weeks is plenty. Each one covers one task, uses a couple of sentences and links to the matching help center article. A long email gets skimmed and the question comes back as a ticket.
Time them to the task
Send the setup email on day one, the first-result email when they are likely to have tried it, and the billing email before the first invoice. Tie them to what the customer did, if your tools allow, rather than to the calendar alone.
Make it easy to reply
Send from a real address that goes to support, not a no-reply. Say plainly that replies reach a person. Some of the most useful tickets are replies to onboarding emails.
Link to the help center
Each email should end with one link to the article that goes deeper. This sends readers to your help center and gives you data on which articles get used.
Check that it works
After a month, compare first-month tickets on the topics you covered with the month before. If a topic still produces tickets, rewrite that email or its article. Drop emails nobody opens or clicks.