Send multiple emails, one at a time, changing address for each

I have a need to send the same email to allot of people, but wanted to ensure that they all received it with out it being blocked by group mailing filters. Here is the resulting script.

On trial I sent 40 individual emails in 3min 20 sec with 9 lines of text and a 300k attachment
I plan on using this script to send 1800 emails probably in groups of 450

Multiple Individual Emails

This code has been created/altered by Joe Sheehan & members of Thank you Mark and Adam.
This code is a descendant from Apple sample code titled "Create new message". 
This code has been provided "AS IS" and the responsibility for its operation is yours.
This script creates a new message, including setting sender,  subject,  recipient,
body, and attachment, to multiple people, one at a time, to ensure the message
is recieved and not blocked by a group mailing filter. 

--direct to your plain text file with addresses, and name, tab delimited
set theAddressDOC to read file ("Macintosh HD:Users:user:Desktop:address.txt")

set pcount to count paragraphs in theAddressDOC
repeat with i from 1 to number of paragraphs in theAddressDOC
	set this_item to paragraph i of theAddressDOC
	set Name_text to "" -- set to blank
	-- using try so if there is a an error, in this case it will be when the is no name, the script will carry on
	-- instead of stopping. The Name_text will reamin as "" if it does
		--use delimiters (tab) in this case to split the result of this_item and try to set Name_text to the name
		set AppleScript's text item delimiters to tab
		set para_text to text of this_item
		--get the second half of paragraph 
		set Name_text to text item 2 of para_text
	end try
	--get the first half of paragraph 
	set address_text to text item 1 of para_text
	--reset the delimiters
	set AppleScript's text item delimiters to ""
	set theAddress to address_text
	-- direct to a doc of what you want the email to say in plain text
	set theletter to read file ("Macintosh HD:Users:user:Desktop:Letter.txt")
	-- What is the subject of the Emails
	set theSubject to "Example"
	-- Check to see if Name_text contains a name or not
	if Name_text is "" then
		--if no name 
		set theBody to "To whom it may concern" & theletter
		--the must be a name 
		set theBody to "Hello " & Name_text & theletter
	end if
	-- add atachment. you need to set the full path. 
       -- If no attachment remove this line and the "make new attachment" line further down
	set theAttachment to alias "Macintosh HD:Users:user:Desktop:Attachment"
	-- Choose the account to send the message from
	set theSender to ""
	tell application "Mail"
		set newMessage to make new outgoing message with properties {subject:theSubject, content:theBody & return & return}
		tell newMessage
			-- Default is false. Determines whether the compose window will
			-- show on the screen or whether it will happen in the background.
			set visible to true
			set sender to theSender
			make new to recipient at end of to recipients with properties {address:theAddress}
			tell content
				-- Position must be specified for attachments
				make new attachment with properties {file name:theAttachment} at after the last paragraph
				tell application "Mail"
					send newMessage
				end tell
                              -- delay to allow the Mail program to send and not bog down, adjust as needed
				delay 4
			end tell
		end tell
	end tell
end repeat