Everyone in email marketing says that readers scan the content. This goes for the Subject line in their inbox as well. Out of the ten or so words presented to them, those in your email lists will register just two or three. Whilst this might seem to be a real obstacle in your path it also leaves opportunities that you can exploit.
There are legal limitations. You cannot mislead recipients, suggesting an offer that does not materialise in the email itself. That said, you should not do that anyway as it is likely to encourage them to unsubscribe.
There are practical limits as well. Do not use all caps or excessive punctuation. Incorrect use of apostrophes can irritate so none is best. Beyond that the content is down to you.
Brevity is essential. In a few words you have to gain the reader’s attention, intrigue them and convince them it is worth opening the email. So not one can be wasted – each word must have a specific purpose.
One mistake many of those engaged in email marketing make is to try and sell the product. That is not the purpose of the Subject line. It should only encourage the email to be opened.
There are good words and bad words. Some are universal. Now, instant, limited, only for: all these put pressure on the reader. Not much but you need to ensure that they do not decide to open the email later as this normally means never.
Ask yourself what word would excite those on your email lists. If you are selling wine then: ‘Last few cases of ’03’ might be just right. If it is a sports bicycle then carbon fibre or perhaps the name of the latest hero of the tours.
Do not wander around a subject. If there is 50% off then tell them so immediately, and what is discounted. Remember that all you have to do is persuade them that they should go further now.
As always there are few hard and fast rules. Obey them and then experiment a little. You will soon get to know what works for you.