As developers attention and focus are very important. I found that email was an attention killer.
Here are the things that I did to use email effectively and avoid losing focus.
I turned off all alerts for email. My phone does not even connect to my email account. Be deliberate about when you check your email.
We forget that email is an asynchrounous tool.
I check my email only at specific times of the day. The two best times I have found are around noon and 4. The exact time is flexible because I don't want to interrupt something I am working on to check my email. Once I have finished what I am working on then I will check email.
Do not check email while waiting for something to complete. It will distract you from your work.
Only check it when you will have the time to process your email.
The process of inbox to zero is best explained elsewhere: https://zenhabits.net/inbox-master-get-all-your-inboxes-to-zero-and-have-fewer-inboxes/
Research has found that it is faster to just archive and search than it is to sort emails into folders and look for an email.
I make two exceptions to the no folders rule. I have a receipts and a waiting folder. I put receipts into a folder because I often need to look at a date range of the receipts.
The waiting folder is for any emails for which I am waiting for a reply.
Use tools to send emails at a later time, especially if you check your emails after normal work hours, this way people wont think you are always checking your email. Use http://boomerangapp.com/ if you use gmail.
Use the "Send it later" plugin for thunderbird.
I sometimes need to write emails during the day, however I dont want view my inbox. You can open a compose window to write an email to avoid being distracted by your inbox.
Thunderbird on Mac:
If you use email as your task list then you can be distracted by your inbox when you look at your task emails.
Make a task list elsewhere.