For the most part, our Gmail filters will work well - but if you're running into problems getting mail blocked, follow these two steps:
Find and block your mail servers
If you're on a corporate or university mail server, you'll need to find the address of your mail servers and add them to the block list. To do this, open up Settings -> Mail, Contacts, Calendars -> Accounts, and select the email account you wish to block. If this is an exchange account, you're going to want to block the "Server." If it is a standard email account, you are going to want to find the SMTP server. If this is too complex, you may want to ask your IT admin for help.
Switch from Push to Fetch
If you don't want new message notifications distracting you, switch your email from Push to Fetch. In Settings -> Mail, Contacts, Calendars -> Fetch New Data, make sure your email account is set to Fetch (not Push).
Blocking email on Mac?
Not iOS - but sometimes people wonder about this as well. If you need to block an email client on a Mac, open up Freedom and choose Options -> Advanced Options, and make sure "Block Email and Chat" is selected.
In addition, our App Blocker (soon to be released) can block individual clients.
Blocking email on Windows?
Email blocking for dedicated desktop clients will be best addressed by our Windows App Blocking feature. This feature will be released for Windows after we release for Mac.
In the meantime, the following rules can be used to block Exchange and Office 365. Please note they may interfere with other Microsoft services. Add these to a blocklist to block Exchange.