Storage-Side Metadata

When saving data to object storage, Dovecot stores metadata associated with each blob for data recovery purposes.

This data is written to the HTTP endpoint by adding Dovecot metadata headers to the request. When retrieving a message from object storage, this data is returned in the received headers (only parsed by Dovecot if needed).

The header name used is specific to the obox driver:

Driver	Metadata Header
azure	x-ms-meta-dovecot_<key>
s3	x-amz-meta-dovecot-<key>
sproxyd	X-Object-meta-dovecot-<key>
swift	X-Object-Meta-<key>

The metacache keys available are:

Key	Description	Max Length (in bytes)	Data Type	Other
username	Dovecot unique username	N/A (installation dependent)	email
guid	Message guid	32	email
size	Message size (in bytes)	20 (in theory; rarely more than 10)	email
received	Received date (unix timestamp)	20 (in theory; rarely more than 10)	email
saved	Saved date (unix timestamp)	20 (in theory; rarely more than 10)	email
pop3uidl	POP UIDL	N/A (depends on source installation)	email	Only if message migrated
pop3order	POP message order	10	email	Only if needed by migration
origbox	Folder guid of first folder where stored(copying does not update this)	32	email
fname	Dovecot filename	N/A - installation dependent (username component)	email	Dictmap only
username	Dovecot unique username	N/A (installation dependent)	index
size	Bundle size (in bytes)	20 (in theory; rarely more than 10)	index
fname	Dovecot filename	N/A - installation dependent (username component)	index	Dictmap only
mailbox-guid	Mailbox guid the index refers to	32	index	Dictmap only
username	Dovecot unique username	N/A (installation dependent)	fts
fname	Dovecot filename	N/A - installation dependent (username component)	fts	Dictmap only