Transient Suppression Lists are custom suppression lists, stored in MD5 Format, that you can add to suppress against when you send emails. 

On the navigation menu under Contacts, click on Transient Suppressions (Fig 1). 

Fig 1

Click on Upload Suppression List (Fig 2). 

Fig 2

On the Upload Suppression List window, upload your file and click on Upload & Save (Fig 3). The only file types we support are CSV and TXT. All that's required are email addresses with no other data fields. Note that your file can contain email addresses in 'normal' and/or 'MD5' format.  The file can contain both formats in the same file.  Ideally, the file should be a single column of data, or a single row of comma separated values.  Email addresses provided in 'normal' format will be converted to MD5 upon upload, so once uploaded, all email addresses in transient suppression lists are stored in MD5 format only.

Fig 3

After the import is complete, you'll see the results on the Import Result window. Click OK to close the window (Fig 4). 

Fig 4

Now when you are sending an email campaign, on the final step under Advanced Settings, click the Select Lists drop-down menu to the right of Prevent sending to subscribers in list (Fig 5).

Fig 5

When you're done, click on Next and on the final Send an Email Campaign page click Schedule My Email Campaign.

If you need to delete a Transient Suppression List, navigate back to Transient Suppressions and click on the trash can icon next to the list you want to delete (Fig 6).

Fig 6

A box will pop up asking if you want to delete this list (Fig 7). Click OK to delete the list. 

Fig 7

If the deletion is successful, a pop-up window will confirm the list is deleted (Fig 8). Click OK to return to the Transient Suppression List.

Fig 8