If you are into email marketing, testing is the key. There are various things to  tested to improve Email Open Rates. Link click through rates is completely different area.

1. Send Email once a week ( on high traffic days)
2. Send Email once number of articles reaches certain number  ( RSS to Email)
3. Generic Email Subject ( What’s New, Free New Articles, 3 Free New Articles, …)
4. Email for every new article ( Once per day)
5. Email Subject to be Article  Title
6. Use Readers name in Email Subject
7. Include Call to Action Words ( Final Call, Open Now, One Day Sale Only, …)
8. Use small caps instead of  Capital letters.
9. Use Symbols to emphasis an idea ( [Download], (Click Now), …)
10. Short email subject line ( sometimes lengty ones work too)

Take one idea, test it for a week and run through all possible combination’s. After you find the subject that works, work to improvise on that.

Example – If sending emails on Mondays mornings has higher open rates, then try other combination’s on Monday.

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2. Send Tweets via Email Using TweetyMail
3. Very High Unsubscribe Rate with Pop-Over Form