How to remove emails from archive from a certain sender / based on tag (4273263)

1.) Create a Tag to be used for the messages to delete, here we use a Boolean Tag

2.) Create a Retention Policy which would delete all emails tagged by this Tag
please mind - in versions 5.5 / 5.6 of Archive Manager, we set Boolean Value to 'True', according to the Tag created in the step before. Known issue exist with this setting in versions 5.3 / 5.4 of Archive Manager where we better set Boolean Value to 'Either' here, to work around the known issue.

3.) Then search for all emails from a certain sender, using Advanced Search

4.) Tick all emails found and click on ‘Tags’ – choose the Tag we created in step 1 and click on ‘Submit’

this action  would then tag all emails found by the search.

Knowledge Article 267298 tells you how you can tag  emails in bulk: 
How to Bulk Tag Emails in Archive Manager 5.4 and higher. (267298)
https://support.quest.com/archive-manager/kb/267298/how-to-bulk-tag-emails-in-archive-manager-5-4-and-higher-

5.) Then you can test the Retention Policy by setting to Safe Mode 

after the Retention run, compare the output of the Execution Log with the amount of found emails

Knowledge Article 42571  tells how you can test the Retention immediately:
How can the Archive Manager Retention Service be forced to run immediately? (42571)
https://support.quest.com/archive-manager/kb/42571/how-can-the-archive-manager-retention-service-be-forced-to-run-immediately-