General-Purpose Mail Package
|Official GNU Software|
POP3 clients often login frequently to check for new mail. Each new connection implies authenticating the user and opening his maildrop and can be very resource consuming. To reduce server load, it is possible to impose a minimum delay between any two consecutive logins. This is called ‘LOGIN-DELAY’ capability and is described in RFC 2449.
As of version 3.5, GNU Mailutils
to set global login delay, i.e. such enforcement will affect all POP3
users. If a user attempts to log in before the specified login delay
expires, he will get the following error message:
-ERR [LOGIN-DELAY] Attempt to log in within the minimum login delay interval
The message will be issued after a valid password is entered. This prevents this feature from being used by malicious clients for account harvesting.
To enable the login delay capability, specify the minimum delay
login-delay configuration statement, e.g.:
pop3d utility keeps each user’s last login time in a
special DBM file, called login statistics database, so to be
able to use this feature, Mailutils must be compiled with DBM support.
By default, the login statistics database is called
/var/run/pop3-login.db. You can change its name using
stat-file configuration statement:
login-delay 60; stat-file /tmp/pop.login.db;
The login delay facility will be enabled only if
able to access the statistics database for both reading and
writing. If it is not, it will report this using
start up without login delay restrictions. A common error message
Unable to open statistics db: Operation not permitted
You can check whether your
pop3d uses login delays by
connecting to it and issuing the ‘CAPA’ command. If login delays
are in use, there response will contain the string ‘LOGIN-DELAY
n’, where n is the actual login delay value.
This document was generated on October 27, 2018 using makeinfo.Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.