Email File Format Options for backups

Question

I am planning to backup emails in a mailbox to files. I am trying to find out the right format based on the following conditions:

• Should be readable/creatable without needing a particular OS - so Outlook file formats are out.
• Should support attachments. (Base64 Encoded is fine)
• Should be reasonably standard (I don't want to back up 5 years of emails before realising there are not clients around to read or process them.)
• Should be possible programatically possible to backup using Crons.

In all likelihood I will code the backup script myself using PHP as the language, but anything that works out of the box on Ubuntu is fine too.

It seems that MBox (https://en.wikipedia.org/wiki/Mbox) seems to be the right option. Is that so? If not what else? If so, any pointers to libraries that operate on mbox that are still supported or in development?

Answer 1

mail files are usually stored in rfc822 format which is used by most mail clients and covers all your requirements. instead of putting them alle in a single a mbox file you might want to consider using one file per mail which makes it faster to restore a single mail (you can easily search based on file time for example) rfc822 mail files usually have a ".eml" ending