Marketers can send more messages without suppressing response, but not necessarily to users' primary accounts, according to email frequency optimization research published by Return Path. This article is copyright 2015 The Best Customer Guide.

Despite technological advances in message delivery, email frequency optimization remains a highly contested topic among marketers and consumer advocates. Consequently, the company the email marketing-related behaviour of more than 600,000 end users over a three-month period to identify the optimal sending frequency based on subscriber engagement.

The findings suggest that each sender's "magic number" - the frequency that generates maximum response without excessive complaints - not only differs among brands but also differs dramatically based on account type, concluding that marketers can indeed send emails more frequently than they already do, but not necessarily to their customers' primary email accounts.

More tolerant than thought
While it is still true that complaints increase and read rates decline with increased frequency, the threshold at which more complaints offset the benefit of more reads is quite high. Return Path focused on the subset of consumers receiving email from at least five commercial senders to discover the relationship between increased frequency and its resulting effect on complaints and read rates.

Among highly active email users, most tolerate up to an average of five messages per week before complaints offset increases in messages read. When users complain by indicating that a commercial message is spam, mailbox providers stop delivering the sender's email to the inbox, effectively ending their email relationship.

The study highlighted an obvious missed opportunity for many brands, concluding that most email marketers simply need to employ more frequency testing to uncover their capacity to send and sell more.

Why not the Primary Account?
One key to optimizing for frequency is segmenting by account type. Return Path identified three distinct groups based on users' overall interaction with email: primary, secondary, and dead accounts.

Primary accounts, the most actively checked, make up only 24% of all email accounts yet they represent 83% of all messages read. While primary users are highly engaged, they are also not shy in voicing their displeasure, accounting for half of total email complaints. As they represent the majority of reads as well as complaints, primary users are the key audience marketers should optimize their programmes for - albeit cautiously. These users are the best critics to market to as they won't hesitate to praise (read, click through) or criticize (complain, unsubscribe) any shifts in frequency.

More tolerant were secondary account holders who interact with their mailboxes less often and represent fewer reads, but are less than half as likely as primary account holders to complain. These subscribers may represent a frequency test audience that marketers can approach less cautiously.

The complete study has been made available from the Return Path website - click here (free registration required).