Any person and/or company that sends commercial email. This can refer to Advertisers (if they send their own emails), Affiliates and Email Service Providers (ESPs). In many cases, large Advertisers will contract Affiliates and/or ESP’s to send email on their behalf.
In regards to OPTIZMO
In the OPTIZMO System, a Mailer is the general term used for anyone that is given access to upload and download lists (which would then be suppressed from that Mailer’s email drop).
Generally the Advertiser gives access to an Affiliate/Affiliate Network or an ESP which are all considered “Mailers” in our system.