One thing I repeat over and over again is to not send mail that looks like spam. Over at the Mailchimp Blog they report some hard data on what looks like spam. The design is simple, they took examples of mail sent by their customers and forwarded them over to Amazon’s Mechanical Turk project to be reviewed by humans.
In a number of cases they discovered that certain kinds of templates kept getting flagged as spam, even when Mailchimp was sure that the sender had permission and the recipients wanted the mail. They analyzed some of these false positives and identified some of the reasons that naive users may identify those particular emails as spam.
When you send a lot of email marketing, even to a totally permission-based double opt-in list, you’re going to get some spam complaints from your recipients. It’s inevitable. Sometimes, it’s because they’re too lazy to click your unsub link, they think the “spam” button is the unsub link, or sometimes it’s because they forgot signing up to your list (maybe because you send infrequently, like me).
And sometimes, when your email is marked as spam, a human from an ISP, or a human from an anti-spam organization, will actually do a manual review of your email […] they look at your email, and they make a split-second decision to “blacklist or not.”
It’s not only the humans that look at the mail and make decisions based on how the mail looks. There are also spam filters that look at how similar mail is to spam and if it’s too similar it will get blocked.
Sending mail that doesn’t look like spam is important. Mailchimp’s research only confirms that fact. Luckily, spammers are often lazy, so it’s not that difficult to design templates and email messages that don’t look like spam.