Set up better newsletter plugin

I have a blog with ALO EasyMail implemented as a newsletter subscriber plugin. It's not working very well. It is not sending out all the mails, it is taking a full day to send out and it is sending out strange content that interferes with the formatting in many mail readers. What I want is a plugin set up that simply sends out all the mails (thousands) right away - it shouldn't take more than half an hour to send. The text must be readable by every common mail reader. The mails include foreign characters, so that could be a challenge: æ, ø and å. It can be sent in TEXT format if necessary, as opposed to HTML. I don't want any special "share on facebook" links or anything like that in the mail - it will just cause spam filters to find the mails suspicious. The project includes setting up a reasonable well functioning subscribe/unsubscribe function. The project ends when I can send out a plain newsletter to ALL the members within no more than an hour.