Greetings, I am developer with more than 15 years of experience in software industry. I have worked in many areas, including mail integration and different general purpose and specialized viewers (for example flash files, pdf, web pages (html), epub).
I have a question on what type of news do you want to display. Are those news taken from certain web sites, or from some other format (pdf, doc)? Will you have rich media content (videos) or just simple text + images?
Will this application be responsible (beside viewing and subscription) for aggregating news from various sorces and sending them to ship mail?
My current idea are two (if you need aggregator as well) standalone applications, one for ship crews, viewing content, managing subscriptions. This application will check mail periodically for sent updates, parse them and make them available for reading.
Another (aggregator) application will be used on main land (on your server for example) it will be responsible for aggregating news from various sources, packing them to certain format and sending to ships.