It's time to get serious about email marketing, according to a new report by Skift. Email marketing has reached maturity, says the industry intelligence firm in its new report entitled Inbox Strategies: The State of E-mail Marketing in the Travel Industry.

The good news for travel marketers is that the number of email users is increasing globally and, even better, open rates are rising - particularly in the mobile space. So it's time for marketers to implement e-mail targeting and personalisation strategies, says Skift.

The key to email marketing is, of course, content. This is where quality really counts. Every time consumers open a message the success of that e-mail, and what happens next, is entirely dependent on the strength of the content.

What's more, the whole concept of email marketing is changing, says Skift. Consumers now exist in a world of pushed content, where it no longer matters how they receive a message from an airline or hotel - be it via e-mail, text, social-media post, app notification, or alert. In fact, today consumers may expect messages to come in multiple ways, all at once.

Against this background, it's up to travel brands to reach consumers in new and innovative ways.

With all this in mind, how does a travel marketer catch the attention of its audience? Econsultancy may have the answer. According to research from Alchemy Worx, specific words used within the subject line of an email are more certain to drive clicks, while others will turn heads - the wrong way.

In the travel sector, the most effective words are 'holiday' and 'voucher', while surprisingly the word 'vacation' has a negative effect on open rates. Other words to steer clear of are 'departing', 'domestic' and 'choice'.

The same study shows that symbols and emojis can also impact engagement. This turned up some interesting findings. For example, a black sun symbol increased open rates by 20.95%, while a white sun caused the rate to drop 8.03% versus the average.

A star increased engagement by 10.65%, but perhaps most surprising is the effect a friendly snowman symbol had on the figures. Apparently this symbol is hugely effective at encouraging people to open marketing emails; it increased the open rate by 65.72% against the average (although Econsultancy rightly questions how effective this symbol is in a subject line in, say, June).

While it's interesting to note which words - and emojis - work best, factoring in the company's tone of voice and target audience will help reinforce email marketing efforts. And it's worth remembering that the open rate is also influenced by other factors, such as sending frequency, time of day and day of the week.