If you're sending content that includes blacklisted URLs, shortened URLs, or content that references commonly-used phrases from spam emails, your emails may generate a failed content review.
Mandrill uses a variety of factors to help set an account's reputation and hourly quota. One of these factors is the content of the email you're sending.
After you remove URLs or other content that results in content review failures, your account reputation and quota will adjust automatically based on the new sending patterns.
How Content Reviews Affect Reputation and Quota
As part of the account reputation and hourly quota system, Mandrill automatically reviews the content of the emails you send. This helps us find potential issues that could harm your reputation as a sender or the reputation of Mandrill's sending IPs.
Like most ESPs, Mandrill actively manages the IP addresses used to send mail through our system. We need to send mail quickly, with as little delay from the receiving servers as possible. The reputation of our IP addresses is paramount to ensuring high deliverability for all users.
Reasons for Failed Content Reviews
- Using shortened URLs. A shortened link is a standard URL that is clipped down to a more manageable size. Most shortened links also hide the destination URL, allowing spammers to trick people into clicking harmful links.
- Linking to content hosted on blacklisted domains. Many ISPs and spam filtering services use blacklists (lists of IP addresses and domains of known spammers, or "spam friendly" servers).
Not all blacklists are created equal. Anyone can create a blacklist and share it with the internet. Most large ISPs only use the most reputable blacklists. This includes SpamCop, Spamhaus, and URIBL, among others.
Reducing or Preventing Failed Content Reviews
If you're using shortened links in emails and seeing a higher number of these emails being sent to spam folders or being blocked altogether, spam filters might signal red flags because of the redirected or shortened links. It's always best to use the full link, as no URL shortening service is perfect and they're all susceptible to security issues or blacklisting.