Spend time and effort on your subject line copy. It may be your one and only split second chance to grab your target's attention.

1. Does it pass the 'must open, must read test'?
   • Review these email formulae that work.
   • When writing your subject line, ask youself:

     Does the subject copy make it clear that the content will be valuable, and so catch the reader’s attention?

     Does it offer a relevant benefit/advantage to the reader?

     Will your reader feel like they are missing out if they don't open it?

   • Distil the core proposition and key benefits into the minimum number of words.
   • Consider including some urgency. Are you announcing something important and relevant to your audience?
2. Have you considered the readers who use ‘auto preview’?

   Make sure that the first 50mm of your email contains compelling copy.
   
   

3. Is your subject line continuing a previous conversation with your audience? If the other emails were recent then they should relate to each other.
   
   

4. What has your pre-mailout test told you? (Test at least one subject line with each campaign)
   
   
5. Have you considered personalising the subject line? Can you be specific to the needs of each individual? Doing this will undoubtedly increase readership.

   How do you plan to use existing customer data to personalise each email?
   
   

6. Should you set a deadline?

   "Order by midnight to get delivery by Christmas", or "Offer finishes on Sunday", or "Only 8 hours to go".
   
   

7. Does it ask a question?
   
   

   People typically feel obliged to answer questions, or at least consider the question for a moment.

   Ideally make the question something that the reader either is already, or maybe should be asking themselves.
   
   

What is the best performing subject line?

The best performing subject line - with a staggering 92% open rate - is the two letters Re:

Next best were Re: Follow Up (90%) and Re: update (89%).  Of course the recipient would be expecting and looking out for these emails, so the high open rate is explainable.

Figures come from ContactMonkey research. They analysed the results from 30 million messages sent from Outlook and Gmail.

"The subject line length is simply the result of the best set of words. The length is the output of the words selected, not the input to selecting the words."  Tim Watson

Ultimately your subject line is acting as a headline - so review this guidance on producing great marketing communication headlines.

Finally, remember that there is no sure-fire formula to success. What works for one type of campaign may bomb in the next. Using the above guidance and testing is ultimately your best route.