iOS7 and mobile emailAccording to a recent report by Experian, more than half of all emails opened take place on a smartphone or tablet. Making sure emails look right and perform as intended on such devices is therefore of primary importance to all email marketers.

Apple’s recently updated mobile operating system, iOS 7, appears to have brought with it a bug which could affect the way in which email subject lines are digested on that particular platform. Some users have reported that the Mail app is now more sensitive to numbers contained within subject lines and, as a result, the way in which it treats them is a little bit unpredictable.

iOS has always been rather clever when it spots dates and times in text by automatically turning them into links, enabling the user to instantly add an event to their calendar (known commonly as ‘event triggers’). It has done this with email subject lines for some time, but the update has proved problematic for some. For example, if an email is sent with the subject ‘Our Sunday 1 day sale is now on’, iOS now turns ‘Sunday 1’ into a link which sends the user to a new calendar event on the 1st of the next month. Obviously, that is entirely incorrect, as the subject line is not referring to that date in particular and the word ‘Sunday’ and number ‘1’ are not linked in that way. More worryingly, some users have tested real dates in subject lines such as ‘Nov 12th’, and reported that iOS failed to turn them into links at all.

However, there are ways to ensure you correctly control these automated event links. If you want the subject line of your next email to turn into an event trigger on iOS, it is best to use the following date format: ‘MMM D’, i.e. the first three letters of the month and the single or double digit numerical date. That is the format Apple appears to have stuck to when looking for event triggers.

Apple have not responded to requests for comment on the matter, but this latest quirk is a timely reminder than email clients are constantly evolving and, as a result, will inevitably continue to hit bumps in the road along the way.