I'm increasingly wary of any company that "auto" subscribes me to email promotions without first asking, or at the least using my previous engagement metrics, to determine how relevant they are to me. In most cases, a company's emails are the most frequent I will interact with that company, and bombarding me with everything you've got to offer reminds me a lot of a sales associate that follows you around the store asking if you need help with every stop you make. I'm more likely to leave the store empty-handed, or to bluntly ask for a little distance, than to pick up one of every recommendation.
Email marketing is still considered a cost effective tool for engaging with your loyal customers, but that doesn't give you the right to abuse it. It's easy to lose them (hopefully at the click of their mouse), so make sure you're losing email subscribers because they no longer have a need for your product or service, not because you're bombarding them.
By my last count, the average number of emails I receive from any single retailer in a given week is at least 4. Between the actual email I signed up for, the recommendation based on items on their site I viewed, the product I abandoned in my shopping cart, the discount, free shipping notice, etc., that's a lot to sort through. And when you consider that we're dealing with an increasingly crowded inbox to start, it can be downright confusing.
Then, you layer in a new series of emails for either a new product or new service offered... I'm getting annoyed just thinking about it.
Combine messages. If you've got enough discount ideas (free shipping, 20% off), combine those messages. A single email with the cost saving enticements is likely going to interest me more than multiple messages. For me, free shipping may not be much of an enticement if the store is within walking distance. For others, maybe it is the most important. Point is, just as email marketing gives you an opportunity to speak to your loyal customers all at once, let them choose what is most important.
Give me a break (or properly set the expectation). With daily deal senders changing what is acceptable in terms of email frequency, don't try to compete if that's not your game. The term "daily deal" already sets the expectation up front, so if you're not one of them, I'm not going to like it if you take liberties and assume I'm ok with you sending me a daily email. Give your customers a break, even if for a day in between emails. Whatever you set your frequency at, stick to it and set that expectation up front. Any deviation from this should be a mind-blowing deal. Otherwise, I'm likely to dismiss the mind-blowing deal or overlook it because I know I'm going to hear from you tomorrow, too.
Ask for permission when a new email promotion is created. If you've got a new email promotion for either new products or services and you think it's relevant to me (I'm assuming you're at least using past engagement metrics to determine this), just ask. Announce the new promotion, product or service to your customers through a single message, but tell them how they can shut it down. Not having a message wasted on those that legitimately aren't interested isn't a bad thing. They'll tell you and they'll appreciate being asked.
I know some of these are a hard sell because there is a real shot at lost revenue by making it so easy to declare disinterest. But as marketers, we've got an obligation to our customers. Short term thinking can damage your credibility and, once all of the dust settles after the holidays, the ones that set the expectation up front, honored it and listened to their customers are going to stand above the rest.