A spam complaint occurs when a recipient clicks on the ‘report spam’ button in their email program.
Mandrill uses a variety of factors to set an account's reputation and hourly quota. One of these factors is the number of spam complaints relative to your overall sending volume.
After you take steps toward preventing spam complaints, your account reputation and quota will adjust automatically based on the new sending patterns.
Target Complaint Rates
In general, industry standards recommend a complaint rate under .1%. When you send email long enough, spam complaints are inevitable, but a large number of complaints can mean that recipients don't recognize why they're receiving your emails, don't recall signing up for email from you, or their email addresses weren't provided directly.
At certain spam complaint thresholds, ISPs may begin routing all your email to spam folders, completely block your email or you as a sender, or blacklist Mandrill's sending IPs. Like most ESPs, Mandrill actively manages the IP addresses that are used for sending mail through our system. The reputation of our IP addresses is paramount to ensuring high deliverability for all of our users.
Reasons for High Complaint Rates
- Using purchased, rented, and third-party lists. These types of lists are bad sources for email addresses because the recipients haven't directly agreed to receive information from you, and may not be expecting your email. They're less likely to read the emails and more likely to mark the messages as spam.
- Not including an unsubscribe link. A spam complaint is a very negative action while an unsubscribe is considered less harmful. Giving recipients the option to unsubscribe or manage notification preferences (even for transactional emails) is recommended.
- Old or stale recipient email addresses. Email addresses have a short lifespan. Recipients change jobs, change names, and create and delete email addresses at will. As a result, email address can become invalid over time, so only send to clean and current addresses to avoid issues with stale lists.
- Sending content that isn’t relevant to your recipients. Your recipients are already inundated with massive amounts of email and spam. If your content resembles spam, doesn’t hold their interest, or isn’t related to their business relationship with you, you run the risk of the subscriber reporting your message as spam.
- Sending too often. Only send transactional email triggered by an action (a purchase, password reset, username reminder, receipt, shipping notification, etc).
Reducing or Preventing Spam Complaints
Provide an unsubscribe link. It may not make sense for recipients to unsubscribe from transactional emails, and most countries only require an unsubscribe link or other unsubscribe process when sending bulk email. But by including an unsubscribe option even in your transactional emails, you can get feedback about how people are engaged with your emails and prevent sending to someone who has signaled they don't wish to receive more emails.
Mandrill provides a List-Unsubscribe header for all emails sent through our system that include our automatic unsubscribe merge tag. The List-Unsubscribe header is a fallback option for recipients who don’t want to receive emails but also don’t want to classify them as spam. If you prefer, you can use your own unsubscribe process or add your own List-Unsubscribe header in your message API request via the
Don't use purchased, rented, or third-party recipient lists. Using a confirmed or double opt-in process is considered an industry best practice, but it's not strictly required. When you use the double opt-in method, you're targeting only those recipients who want to hear from you. Double opted-in lists have much higher engagement levels over time which translates to more opens and clicks and fewer spam complaints and bounces. You should always ensure that you're only sending to recipients who have a prior business relationship with you or who have consented to receiving emails from you.
Use a relevant reply-to email address. When setting the Reply-To header for your emails, be sure that you or someone in your organization has access to this email's inbox and that the address matches the message content or your application/business.