More than one in six emails (17%) sent by marketers do not reach consumers' inboxes: 11% simply go missing and another 6% land in spam/junk folders, according to a recent report from Return Path.

The report was based on an analysis of 492 million commercial messages sent with permission to consumers around the world between May 2013 and April 2014.

The proportion of emails that didn't arrive in inboxes stayed fairly consistent throughout the time period examined, including during the end-of-year holiday shopping season when email volume typically surges.

Below, additional key findings from the report.

Inbox Placement by Country

Inbox placement rates vary significantly by country, the analysis found. For example, in the 12-month period examined, European marketers struggled more than North American marketers with missing messages but they had less mail routed to subscribers' spam folders.

Brazilian senders had the hardest time connecting with subscribers, reaching the inbox only 60% of the time, with nearly one-third of their messages disappearing altogether.

Inbox Placement by Industry

The industries most dependent on consumer relationships, whether for direct sales or transactional updates, tend to have better inbox placement rates, the analysis found. For example, retailers (including apparel and health/beauty marketers) had more than 90% of their emails arrive in inboxes during the time period examined.

Financial services companies, including banks and insurers, also reached customers’ inboxes more consistently than others, whereas publishers, media/entertainment providers, and tech companies had more messages than average end up lost or in spam/junk folders.

About the research: The report was based on an analysis of 492 million commercial messages sent with permission to consumers around the world between May 2013 and April 2014.