When comparing Nine vs Blue Mail, the Slant community recommends Blue Mail for most people. In the question“What are the best Gmail clients for Android?” Blue Mail is ranked 3rd while Nine is ranked 10th. The most important reason people chose Blue Mail is:
Offers a lot of different preferences (like Quiet Hours, Custom Sounds, Vibrate, LED Light, Snooze Alerts, etc.). You can set different preferences for each of your accounts.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Can adjust color themes for each account.
Pro Supports ActiveSync protocols
Pro Convenient theme options
The black theme is easy on the battery and eyes.
Pro Good customization
But not so many you have to read and dig through documentation to do what you want.
Pro Supports Outlook category colors, Outlook for Android doesn't
Pro Very reliable
Pro Highly customizable notifications
Offers a lot of different preferences (like Quiet Hours, Custom Sounds, Vibrate, LED Light, Snooze Alerts, etc.). You can set different preferences for each of your accounts.
Pro Integrated calendar
Pro Supports multiple e-mail accounts
Gmail, Yahoo Mail, Outlook, Alto, iCloud, Office 365, IMAP, POP, etc.
Pro Unified inbox
Pro Clustering of e-mails by sender
Pro Supports Android Wear
Cons
Con Not free
Con Not Cross-platform at all
Only has an Android app. No Windows, Mac versions available.