Recurring Postfix/master "fatal: bind: error" with smtpd

Re-posting this in the Mountain Lion community (inadvertently posted it in the Snow Leopard community):

Hi; I hope someone can help me with this recurring Postfix/master error that recently cropped up.

I keep seeing the following Console messages (the PID numbers should give you an idea of how many recurrences have happened - seems to be every 10 seconds):

3/29/15 7:40:35.574 PM postfix/master[20221]: fatal: bind: private/smtpd: No such file or directory

3/29/15 7:40:36.575 PM com.apple.launchd[1]: (org.postfix.master[20221]) Exited with code: 1

3/29/15 7:40:36.575 PM com.apple.launchd[1]: (org.postfix.master) Throttling respawn: Will start in 9 seconds

3/29/15 7:40:45.584 PM postfix/master[20224]: fatal: bind: private/smtpd: No such file or directory

3/29/15 7:40:46.585 PM com.apple.launchd[1]: (org.postfix.master[20224]) Exited with code: 1

3/29/15 7:40:46.585 PM com.apple.launchd[1]: (org.postfix.master) Throttling respawn: Will start in 9 seconds

3/29/15 7:40:55.593 PM postfix/master[20225]: fatal: bind: private/smtpd: No such file or directory

3/29/15 7:40:56.595 PM com.apple.launchd[1]: (org.postfix.master[20225]) Exited with code: 1

3/29/15 7:40:56.595 PM com.apple.launchd[1]: (org.postfix.master) Throttling respawn: Will start in 9 seconds

Any suggestions about how to put a stop to this?

Thanks, - M.