Incremental method for backup of email messages

A system comprising:

• one or more processors;
• a memory coupled to the one or more processors and configured to store program instructions executable to implement:
• a mail server configured to store mail messages in a mail folder object;
• a backup application configured to perform a full backup of the mail folder object, wherein to perform the full backup the backup application is further configured to:
• store a version of at least some of the mail messages in the mail folder object to a backup medium;
• store a backup time corresponding to a start time of said full backup in the mail folder object;
• store a version of at least some of the mail messages in the mail folder object to the backup medium dependent upon whether the at least some of the mail messages include a corresponding attachment;
• store the version of the given message on the backup medium in response to determining that the given message includes the corresponding attachment, wherein the version of the given message includes an attachment identifier and excludes the corresponding attachment;
• and
• store metadata associated with the corresponding attachment in an entry of an attachment index, wherein each entry in the attachment index corresponds to a respective attachment for which no other entries are included in the attachment index.

A computer readable storage medium storing program instructions executable to implement:

• a mail server storing mail messages in a mail folder object;
• a backup application performing a full backup of the mail folder object, wherein performing the full backup comprises:
• storing a time the full backup begins as a backup time in the mail folder object;
• the backup application transferring a version of at least some of the mail messages in the mail folder object to a backup medium dependent upon whether the at least some of the mail messages include a corresponding attachment;
• the backup application storing the version of the given message on the backup medium in response to determining that the given message includes the corresponding attachment, wherein the version of the given message includes an attachment identifier and excludes the corresponding attachment;
• and
• the backup application storing metadata associated with the corresponding attachment in an entry of an attachment index, wherein each entry in the attachment index corresponds to a respective attachment for which no other entries are included in the attachment index.