So, what is the ‘best’ length for the Subject line in an email? Perceived wisdom is that 50 characters is the outer limit, with best practice limiting you to 45. There have been some bulletin board exchanges about 200-plus character length Subject lines (including one test involving a 1500 character line). But an email Subject line is a bit like a Porsche Cayman: the fact that you can accelerate from 0 to 62 miles an hour in 6.1 seconds doesn’t mean you should.

In the summer of this year, digital marketing agency Alchemy Worx carried out some interesting research that indicated Subject lines of less than 60 characters were best for optimising open rates, while click
and click-to-open rates were optimised by subject lines of over 70 characters. There was a ‘dead zone’ between 60 and 70 characters that didn’t optimise anything.

What interests us here at the CDA Content Lab is how people are engaging with Subject lines? We know that, online, people tend to scan and skim text in a very visual way. This is different to the character and shape decoding that goes on when we settle to read (which we may do online at certain arrival points, but more on that another time).

We also know that From lines are very important when it comes to opening emails, as people try to tackle ever more full inboxes. From lines are more manageable and often more unequivocal than Subject lines. We see a name we recognise, so we open the email. We always advise clients to spent as much time on the From line as on the Subject line. From the Acme Trading sales team may be much more openable that From Fred Bloggs@acmetrading.com if I’ve heard of Acme Trading but I don’t know Fred Blogs from Adam.

So some degree of familiarity – resonance – works in the From line. Can we work this little benefit into the Subject line? What do recipients want to see in their From lines? Keep in mind we’re discussing a business-to-business and business-to-customer / prospect environment here. From lines to mates and relatives are a whole other ball of wax.

What we’re working towards is reply-focussed communication (see our earlier post). In email and website content we’re often engaged in conversations with people we have never met and who we can’t hear. We have to anticipate what they want and reply accordingly. So…

If I get an email, which is not a regular newsletter I’ve subscribed to, I want to know ‘why?’. Keep in mind that spammers are exploiting the ‘why?’ card, so go for something that’s clear and quick to understand, coupled with a good From line that underpins your authenticity. Clients occasionally talk about the ‘wow’ factor but my advice is that ‘wow’ is often very spammy.

When an email newsletter hits my inbox I want so see news. I’m not reading at this stage, so it is possible to get away with words like ‘latest’ and ‘update’ so long as there’s a robust context. ‘Latest news’ just doesn’t cut it without explaining what the latest news pertains to.

If it’s an email from a product provider, then an offer always goes down well – again, give me context.

I’d also hypothesise that, because the recipient isn’t reading that this stage, you can get away with something less than correct sentence construction. Even a simple sentence is a complex beast and I’m not going to get sidetracked by explaining subjects and predicates and goodness knows what else at this stage.

An email Subject line needs a whole new rule book. The ‘object’ of the Subject line is the recipient of the email. Oh goodness, all the grammarians have just fallen over!

You don’t have to place the object in the Subject line. That said, adding the recipient’s first name to a Subject is an increasingly deployed bit of conditional content.

Think about shape. As I’m scanning and skimming, give me short, familiar words that convey clear meaning. It’s worth drawing up lists of words you use frequently in your emails. Type them down, all in the same font, all lower case and the same size and then scan them with your eyes half closed. Which ones leap out at you?

Finally, think about length. If you want to, divide the Subject line into pre-35 and post-35. Put the main point of your email in the first 35 characters and use some additional length to develop a supporting argument or an action eg ‘read our 10 top tips about this’.

And remember, size isn’t everything.