In order to use this feature you must register with major ISPs in order to receive notifications by email about subscriber complaints.
Note that this is different from the complaints sent by your smtp service such as Amazon SES, MailGun, SendGrid, Mailjet and which you can capture using dedicated webhooks (no plugin required).
You create an email account specifically for this purpose. ISPs will send you email notifications to this mailbox.
If possible you should ask the ISP to send you back the original email you sent (attached) or its headers.
evoMailer will scan this mailbox and try to extract subscriber and campaign information. Do not download these emails from the server (or leave a copy if you do). evoMailer deletes them after processing.
What will evoMailer do with these emails: - Create an entry in your complaints table. - Update the subscriber account with related details. - Automatically suppress the subscriber depending on your automatic suppression threshold.
Processing is automated with cron job #11. See details.