Sendmail, 3rd Edition

The mail.local Delivery Agent

The mail.local program is a delivery agent designed to replace the normal delivery agent on many, but not all, versions of Unix. Read the file mail.local/README for up-to-date information about how to determine if your version of Unix will support mail.local.

On systems that support it, the mail.local program’s chief advantage over your standard local delivery agent is that it can use LMTP for local delivery.^[5] With LMTP, delivery of a single envelope to multiple recipients is more robust. LMTP is similar to SMTP, but it is designed for local delivery. It uses an acknowledged protocol that allows each recipient’s status to be reported individually.

Build mail.local

Before building mail.local, you need to decide whether certain definitions should be in your m4 build file.^[6]

When porting to a new system, for example, the maillock(3) library routine for locking user mailboxes prior to delivery might be needed. If so, you will need to define two items in your m4 build file:

APPENDDEF(`conf_mail_local_ENVDEF', `-DMAILLOCK')
APPENDDEF(`conf_mail_local_LIBS', `-lmail')

Here, the first line tells the compiler to include support for maillock(3) as the means to lock local mailboxes for delivery. The second line tells the linker that the maillock(3) and related subroutines are located in the /usr/lib/libmail.a library.

Some versions of Unix require that the mailbox files be group-writable. You can tell if this is true for your site by changing to the directory ...