Monitor Inbox Delivery

You can't rely on bounce reports to identify all inbox delivery problems, particularly at domains like hotmail.com and bellsouth.com. Even if your reports show unalarming bounce rates, most of your email could have been deleted before ever reaching your subscriber's inbox or bulk folder. That occurs when a domain pays a third-party (e.g., Brightmail) to intercept and delete mail that doesn't meet their criteria without informing the domain (doesn't want to know) nor the mailer (doesn't care about the mailer).

So, to track deliverability manually, start by analyzing your email list to determine which domains host email accounts for at least 5% of your recipients. Usual suspects include:

Register for several accounts at each of these important domains and "seed" your mailing lists with these email addresses. At least 24 hours after distribution, review each of the "seed" accounts to check for:

If a new problem occurs at a domain, re-test. For validation, also analyze the results for the mailing as a whole, to check for changes in the view and click rates for subscribers at the suspect domain compared to other domains. For instance, if your historical view rates at hotmail were 38%, but have now dropped to 6%, without a proportional decline at other domains, then you've got a new problem at AOL.

If the new problem persists, take corrective action quickly.