Automatically Save emails to a folder using Mail.app, AppleScript, and Bash.

README.md

How to get it to work.

NOTE: This is mac only.

1. Go to Finder.
2. Press CMD+SHIFT+G.
3. Type ~/Library/Application Scripts/com.apple.mail.
4. Open saveByRule.scpt and change theFolder to where you'd like emails to be saved.
5. Copy and Paste saveByRule.scpt into ~/Library/Application Scripts/com.apple.mail.
6. Go to Mail>Preferences>Rules>Add Rule.
7. Enter some filter for your rule and choose Run Applescript as action to perform. Use saveByRule as option.
8. Click Ok.

For converting to PDF and HTML.

1. In the terminal, run sudo pip install mail-parser and brew install Caskroom/cask/wkhtmltopdf.
2. Open toPDF.sh and alter location to match the directory your saved emails are located. (Keep *.eml)
3. In the terminal, run bash toPDF.sh.

For Automating conversion to HTML/PDF.

1. Create new>Folder Action in Automator.
2. Set folder to watch to folder where emails are saved.
3. Add run shell script action.
4. Copy and paste contents of toPDF.sh into textarea of run shell script.
5. Save.

NOTE: saveByRule.scpt is almost entirely copied from StackOverflow.

saveByRule.scpt

using terms from application "Mail"
	on perform mail action with messages theMessages for rule theRule
		tell application "Mail"
			set msgs to selection
			
			if length of msgs is not 0 then
				
				set theFolder to (system attribute "HOME") & "/Downloads/"
				
				repeat with msg in msgs
					set msgContent to source of msg
					-- determine date received of msg and put into YYYY-MM-DD format
					set msgDate to date received of msg
					-- parse date SEMversion below using proc pad2()
					set {year:y, month:m, day:d, hours:h, minutes:min} to (msgDate)
					set msgDate to ("" & y & "-" & my pad2(m as integer) & "-" & my pad2(d))
					
					-- assign subject of msg
					set msgSubject to (subject of msg)
					
					-- create filename.eml to be use as title saved
					set newFile to (msgDate & "-" & msgSubject & ".eml") as rich text
					set newFilePath to theFolder & newFile as rich text
					
					set referenceNumber to open for access newFilePath with write permission
					try
						write msgContent to referenceNumber
						delete msg
					on error
						close access referenceNumber
					end try
					close access referenceNumber
					
				end repeat
				
			end if -- msgs > 0
		end tell
	end perform mail action with messages
end using terms from

on pad2(n)
	return text -2 thru -1 of ("00" & n)
end pad2

toPDF.sh

#!/bin/sh

# if [ -z $(pip list | grep -F "mail-parser" ) ]; then
#     pip install mail-parser || sudo pip install mail-parser
# fi

# if [ -z $(brew cask list | grep -F "wkhtmltopdf" ) ]; then
#     brew install Caskroom/cask/wkhtmltopdf
# fi
location=~/Downloads
for file in $location/*.eml;
do
    echo $file
    name=${file##*/}
    noeml=${name%.eml}
    echo "$noml"
    mailparser -f $file -b > $location/$noeml.html
    x=$noeml.html
    wkhtmltopdf $location/$x $location/$noeml.pdf
done

# Uncomment any these if you'd prefer not to keep a file type.
# rm -f *.eml
# rm -f *.html
# rm -f *.pdf

Hey @lcn2 these are all awesome suggestions and you're totally right about the security implications of this approach. Since writing this, I've actually shifted to a yearly export as an .mbox that I backup instead. In practice searching through my emails more than a year ago has been a rare occurrence.

That being said! If I were to come back to this, I'd probably try and do my best to keep the eml contents in memory and then pass it into a language like Python as soon as possible so that these kind of protections, looping, deduplicating would be much easier :)

Thanks @dustinknopoff