Email marketing can work very well for some businesses but there is a way in which they often tend to work and a way in which they often fail. Emailing to your own existing database is often likely to get you more response than emailing through to a bought in list of random email addresses. Many email marketing companies also specify that you can only use a list of opted in email addresses and not ones that you have obtained elsewhere.
The subject line is vital on an email as it is often the first thing the viewer will read and can be the deciding factor between opening the email and deleting it. Knowing what to put on a subject line can be tricky and you must remember to restrict the number of characters as much as possible to allow the full title to show. You may intentionally only want part of the title to show so people are intrigued and click to read it, but if doing this, make sure that you take in to account all mail handlers. The subject line should be short, snappy and want to make the reader find out more, often it can be personalised to include their name too.