The mc Configuration Syntax

Under V8 sendmail’s mc configuration technique you include delivery agent definitions in your configuration file using the MAILER( ) mc command. The form for that command looks like this:


For example, SMTP and UUCP support can be included in your file by using the following two commands:


If you include MAILER definitions for procmail, or uucp, those definitions must always follow the definition for smtp. Note, too, that any modification of a MAILER definition (as, for example, with UUCP_MAILER_MAX) must precede that MAILER definition:

define(`UUCP_MAILER_MAX', `1000000')        here
define(`UUCP_MAILER_MAX', `1000000') not here

The delivery agent M definitions that correspond to MAILER( ) commands are kept in the cf/mailer directory.

In general, the files in the cf/mailer directory should never be modified. If one of the definitions needs to be tuned, use the special keywords described under the individual delivery agent equates (Section 20.5). For example, the following line modifies the maximum message size (the M= delivery agent equate, M=) for the UUCP agent:


Here, the maximum size of a UUCP message has been increased from the default of 100,000 bytes to a larger limit of 1,000,000 bytes.

Choose Preferred Agents

Four mc configuration macros are available, beginning with V8.10 sendmail, to help you choose the delivery agent you prefer in various situations.


Get Sendmail, 3rd Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.