We’ve come across a few email marketing campaigns recently which display a very strange issue – for a few recipients a random character, usually an exclamation mark (!) would be inserted at a seemingly random point in the message.
We spent quite some time looking into this and discovered that some mail server/email client combinations have real issues if the length of a line in the HTML code of an email message exceeds 990 characters. At this point the message is forcibly broken with a new line and the insertion of the random character.
No, we have no idea why 990 is special, but it seems to be the magic number.
The good news is that it’s an easy fix – simply view the source of your email campaign and break up any really long lines with a line break.
The better news is that we’ve added this to the long, long list of email client ‘quirks’ that our new email campaign designer automatically fixes on-the-fly, so if you’re using that to create your emails it’s not something you need to worry about at all any more!