Design the message around the customer's next step
Use a clear subject and put the purpose near the beginning. Show the relevant reference, explain what happens next and provide a working route for replies. A logo should support the identity without overwhelming the message. Review both the HTML presentation and plain-text alternative, including links, names and punctuation. Templates should make missing information obvious rather than sending a blank or misleading placeholder to the customer.
Validate delivery as well as appearance
The sender domain, mail service and application settings work together. Confirm the authorised sender and reply address, then test a real message through the configured workflow. Distinguish an attempted send from an actual received message, and review delivery failures without exposing credentials in logs. Agree who can change templates or SMTP settings. Where a message is triggered automatically, confirm recipients and duplicate handling so retries do not become repeated customer emails.