This workflow will move nominated Mail messages to a Mailbox, save attachments to a Finder Folder and cull Mail Messages older than the nominated date from the Mailbox

Move Messages, Save Attachments & delete old Messages.applescript

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# Title:  Move Messages, Save Attachments & delete old Message
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# Iain Dunn
# Logic2Design
# www.logic2design.com
# logic2design@icloud.com

# Last update: 11 July 2022
# Version: 2 - added check for attachment being downloaded

# Contributors and sources
# https://macscripter.net/viewtopic.php?pid=209404#p209404
# Orpy - https://talk.automators.fm/t/deleting-emails-from-mail-on-a-schedule/14037

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# Configuration
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set parentFolder to (path to desktop folder) as string -- The location you want to use to create the Finder Folder to store the Attachments, use path to "docs" to use the Documents folder
set folderName to "Security Driveway" -- The Mailbox and Finder Folder you want to create
set mailAccount to "Fastmail" -- The Mail account you want to use to store the Messages
set mailSubject to "Driveway" -- The keyword you are looking for in the Message Subject
set attachmentExt to ".jpg" -- The attachment type you want to process
set deleteAge to 7 -- After this many days the messages will be deleted

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# Code
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--Create Mailbox if it doesnt exist
tell application "Mail"
	tell account mailAccount
		set folderName to folderName
		if not (exists mailbox folderName) then
			make new mailbox with properties {name:folderName}
		end if
	end tell
end tell
--Move Message & Save Attachments
set attachmentsFolder to parentFolder & folderName & ":"

my makeNewAttachmentsFolder(parentFolder, folderName)

tell application "Mail"
	set messageList to every message in inbox whose subject contains (mailSubject as list)
	try
		ignoring case
			repeat with theMessage in messageList
				repeat with theAttachment in ((theMessage's mail attachments) whose (its name ends with attachmentExt))
					if (downloaded of theAttachment) then -- check if file is already downloaded 
						set originalName to name of theAttachment
						my makeNewEmptyFile(attachmentsFolder, originalName)
						save theAttachment in file (attachmentsFolder & originalName)
					end if
				end repeat
				set mailbox of theMessage to mailbox folderName of account mailAccount
				delay 3
			end repeat
		end ignoring
	end try
end tell
--Delete old Messages
tell application "Mail"
	tell account mailAccount
		set mailBin to mailbox "Trash"
		set selectMessages to messages of mailbox folderName whose date received < ((current date) - (days * deleteAge))
		repeat with m in selectMessages
			move m to mailBin
		end repeat
	end tell
end tell
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# Functions
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on makeNewAttachmentsFolder(parentFolder, folderName)
	try
		tell application "Finder" to make new folder at folder parentFolder with properties {name:folderName}
	end try
end makeNewAttachmentsFolder

on makeNewEmptyFile(attachmentsFolder, newFileName)
	try
		tell application "Finder" to make new file at folder attachmentsFolder with properties {name:newFileName}
	end try
end makeNewEmptyFile