There's a reason for me saying “Hey” in title which may surprise you…)

In the last presidential race, almost all of Obama's $690m funding came from fundraising emails.

And it turns out that his campaign team were obsessively testing different types of email behind the scenes.

They'd send out test emails to a sample of supporters with different variations of subject lines, amounts asked for – even fonts and buttons. Whichever raised the most money was then used as the main email to send to everyone else.

And they found out some pretty interesting stuff that we can all definitely learn from.

Firstly, a causal tone worked best. After the election was over, Toby Falsgraff, Obama's email director revealed that “The subject lines that worked best were things you might see in your in-box from other people”.

Nothing clever. No screaming headlines. Just emails that looked and felt like they came from your friends and colleagues.

In fact their best-performing headline way simply “Hey”.

Dropping in the odd mild profanity worked too. Again showing that we respond best to emails written to sound like human beings talking to us – not formal corporate speak.

And they also found that people were very happy to receive plenty of emails. “At the end, we had 18 or 20 writers going at this stuff for as many hours a day as they could stay awake. The data didn't show any negative consequences to sending more.”

So here's the thing. If frequent, casual emails work best for the president's supporters to raise the most funding – might something similar work for you?

When I work with clients on email marketing their initial fear is often that they need to send “professional” emails (and professional usually means boring and stiff).

But every time we test it we find that more casual emails – written to a “good business friend” get a much better response.

Try it.