How do I upload a suppression list on Opensend to exclude existing emails which we don't want Opensend to capture?

Suppression lists can be added manually to Opensend, as described below, or can be updated programmatically via API, as described here.

1. Go to the “Settings” tab
2. Click on “Suppression List”
3. From the “Suppression List” tab you can add any email manually and select a comment/reason for its exclusion. A custom comment can be added as well from the dropdown. 
   Note: Multiple emails can be added by separating them with a semicolon (;)
4. Press Save button 
   
5. From the “Bulk Action” tab you can upload a csv list of emails you want to exclude
   Note: The maximum CSV file size allowed to upload is 100 MB (~3 million emails). If your CSV is too large, simply divide it into pieces, or consider adding to the suppression list via the API.
6. The csv sheet should contain only one column i.e. email and list of emails under that
   
7. Click on upload a file and select the file
8. Under comment dropdown select reason for exclusion
9. Press Save button