Mail servers: technical details
Passwords are generated with the dovecot-doveadm utility:
/usr/bin/doveadm pw -s CRAM-MD5 -u <email address>
Delivering email to a user mailbox
dovecot-lda is set by the SMTP-server as the default mail transfer agent.
The utility performs the following steps:
- When the email is sent from the SMTP-server, the utility gets the information about the mailbox from the file /etc/dovecot/dovecot-passwd.
- The utility executes the setuid command to drill down to the mailbox owner level.
- The utility checks the user's disk quotas:
- Specifies the email size in <mailbox directory>/.maildir/maildirsize.
- Calculates the total mailbox size.
- Compares it with the quota specified in dovecot-passwd. If the quota is exceeded, the email will be rejected.
- If the sieve plug-in is connected, the utility checks that the filter file-script is present (.dovecot.sieve per default). If the file exists, it will be executed.
Checking disk quotas
Execute the command to check your disk quota usage:
/usr/bin/doveadm quota get -A
SpamAssassin settings are kept in /etc/mail/spamassassin/local.cf. The main parameters:
required_score — what score is needed to flag an email as spam. The minimum value is 0, the maximum — 100. The default value is 5;
rewrite_header — a header that will be added into the "Subject" field if the email is flagged as spam;
report_contact — contact email. It is added into the spam report.