3.15.1 Database Formats

The version 9.0 runs the following database types (or formats):

‘cache’

Cache database keeps the information about external emails, obtained using sender verification functions (see Checking Sender Address). The key entry to this database is an email address or email:sender-ip string, for addresses checked using strict verification. The data its stores for each key are:

1. Address validity. This field can be either success or not_found, meaning the address is confirmed to exists or it is not.
2. The time when the entry was entered into the database. It is used to check for expired entries.

The ‘cache’ database has two expiration periods: a positive expiration period, that is applied to entries with the first field set to success, and a negative expiration period, applied to entries marked as not_found.

‘rate’

The mail sending rate data, maintained by rate function (see Rate limiting functions). A record consists of the following fields:

timestamp

The time when the entry was entered into the database.

interval

Interval during which the rate was measured (seconds).

count

Number of mails sent during this interval.

‘tbf’

This database is maintained by tbf_rate function (see TBF). Each record represents a single bucket and consists of the following keys:

timestamp

Timestamp of most recent token, as a 64-bit unsigned integer (microseconds resolution).

expirytime

Estimated time when this bucket expires (seconds since epoch).

tokens

Number of tokens in the bucket (size_t).

‘greylist’

This database is maintained by greylist function (see Greylisting). Each record holds only the timestamp. Its semantics depends on the greylisting implementation in use (see greylisting types). In traditional implementation, it is the time when the entry was entered into the database. In Con Tassios implementation, it is the time when the greylisting period expires.