Alternativas ao Dashingmail para Software as a Service (SaaS) com licença de código aberto

• Software as a Service (SaaS)
  Todas as plataformas Windows Mac Linux Android iPhone Apple Watch iPad Android Tablet Windows S Web Self-Hosted Software as a Service (SaaS) MailWizz EMA Amazon SES (Simple Email Service)
• Licença Open Source
  Qualquer licença Licença gratuita Licença Open Source Licença comercial