Archiving email can be a painful experience. Simplify your life with Email Archiver
Email Archiver - with this application you can archive and store all your emails or individual emails in PDF format. The convenience of using this approach is undeniable, because Mail.app itself is not required to read mail messages.
All mail correspondence is stored in a hierarchical manner, i.e. exactly as it is stored in Mail.app. The name of the PDF file is formed from the headers of the mail messages, and the PDF file is created for each message separately. You can create separate folders for your favorite or business emails. For emails with attachments, a separate folder for attachments is created.
Notably, Email Archiver offers the ability to exclude certain folders and select specific directories as the source of email messages. The application pulls data from your library folder and you will need to manually define the appropriate folders.
Last but not least, Email Archiver can be used to permanently backup email accounts: after the initial export, the application will only add new email messages, thus greatly reducing processing time.