Our open rates were approximately 15% when we sent emails (with a fresh blog article) once every two to three weeks.
The open rates more than tripled to around 50% when we started publishing and emailing once a week.
Making a habit of showing up in your readers’ life will keep them interested and motivated to read your material. Your emails are just another aggravation they weren’t expecting because they are unpredictable and frequently go missing from their inboxes for weeks at a time.
Source Unbounce.com