Mailster offers by default two delivery methods:
Additionally, you can add more methods with plugins.
This is the default method and is not recommended for bulk mailing in general. Often providers limit the number of emails that can be sent with this method to prevent spammers. Talk to your host about the limits and if you are allowed to send emails in bulk. Problems?
This is the method you should use if you have many subscribers. Contact your host for the credentials. SMTP requires certain ports to be open. Problems?