What are common root causes of deliverability problems?

Frequent root causes:

List quality issues:

Purchased or harvested lists

Old, unengaged addresses

Spam traps

Invalid addresses

Authentication problems:

Broken SPF, DKIM, DMARC

DNS configuration errors

Alignment failures

Reputation damage:

High complaint rates

Blocklist listings

Low engagement patterns

Sending practice issues:

Volume spikes without warmup

Irregular sending patterns

Poor segmentation

Content problems:

Spam trigger words

Suspicious links

Poor formatting

Most problems trace back to one or more of these categories.

Cargo problems, ship problems, captain problems, or navigation problems. Most incidents fit these categories.