TWC uses Cloudmark that factors in customer complaints, IP sending reputation and content in filtering decisions. It scans email for spam-like characteristics and compares your email to your previous emails to help determine filtering decisions. One of the best ways to reach the inbox, is sending relevant content that your subscribers want to receive. Low complaint rates and having subscribers marking your email as “not spam” signals TWC that you are less likely a spammer.
- Check if your IP addresses have Forward Confirmed Reverse DNS (FCrDNS): IP addresses without FCrDNS will have difficulty reaching the inbox.
- Determine if your content contains a spammy Cloudmark fingerprint: TWC uses Cloudmark in their filtering decisions. After identifying and fixing the cause for the spammy fingerprint, submit a reset request. If you don’t fix the cause of the issue, your content is likely to be marked with a spammy fingerprint in the future.
- Determine if your IP addresses are on Blacklists. TWC uses the following blacklists in their filtering decisions. If your IP address is listed, refer to the Blacklist listing criteria and fix the cause.
- Check your SMTP logs for clues regarding the issue. TWC blocks email with its own real-time block list. If your email is being throttled or blocked, check your SMTP logs for a response indicating a possible cause. AUP = Acceptable Use Policy.
- AUP#1310: Cloudmark related error indicating a 5 minute rate limit block
- AUP#1320: Cloudmark related error indicating a 1 hour rate limit block
- AUP#1330: Cloudmark related error indicating a 24 hour rate limit block
- AUP#I-1010: Indicates a perceived policy violation and possible blacklisting
- Determine if your email authentication is working properly. A misconfigured SPF or DKIM record can result in being filtered or blocked at TWC.
- Check your connection and throughput settings and SMTP error logs to see if you are sending too much email to their servers. Reduce the settings if throttling occurs.
- Check your retry settings and increase time between retries if still experiencing throttling issues. You may want to limit the number of retries per message to 2 or 3 temporarily if needed until you can isolate a cause of the deliverability problems.