Email Distribution Software

I am in need of a bulk email service that will allow for the distribution of newsletters. The niche is pharma and it has to be in the inbox and not in spam folders strictly!

Key Requirements:
- Email software capable
- Simple interface for ease of use
- Ability to segment audience for customized newsletters

Ideal skills and experience for the job:
- Proficiency in email marketing software
- Prior experience with newsletter distribution
- Experience in audience segmentation

Please note that this project is time-sensitive.