Email marketing best practices

Consent, frequency and content that keep people subscribed.

Permission first — only email people who asked to hear from you, and make unsubscribing easy (Reepio adds the link for you).
Be consistent — a predictable schedule beats bursts of email.
Subject lines — specific and honest; avoid all caps and misleading claims.
One goal per email with one clear button.
Clean your list — suppress people who haven't engaged in months instead of emailing them forever.