Daily error mail: duplicate log entry for /var/log/mail/mail.log

[Starbix]

Context

I get a daily email that says that there's a duplicate entry.

I think this happens because there's /var/log/mail/mail.log in both /etc/logrotate.d/maillog and /etc/logrotate.d/rsyslog

Expected Behavior

No error mails.

Actual Behavior

I get a daily mail with the following content:

/etc/cron.daily/logrotate: 
error: rsyslog:13 duplicate log entry for /var/log/mail/mail.log 

Possible Fix

Removing either /etc/logrotate.d/maillog or the mail.log entry in /etc/logrotate.d/rsyslog

Steps to Reproduce

1. Happens automatically

Your Environment

• Amount of RAM available: 72 GB
• Mailserver version used: latest (as of 31.3.18)
• Docker version used:

Client:
 Version:	17.12.1-ce
 API version:	1.35
 Go version:	go1.9.4
 Git commit:	7390fc6
 Built:	Tue Feb 27 22:13:43 2018
 OS/Arch:	linux/amd64

Server:
 Engine:
  Version:	17.12.1-ce
  API version:	1.35 (minimum version 1.12)
  Go version:	go1.9.4
  Git commit:	7390fc6
  Built:	Tue Feb 27 22:20:43 2018
  OS/Arch:	linux/amd64
  Experimental:	false

• Environment settings relevant to the config: All mails to unknown accounts get redirected to the admin.

[akmet]

Will have a look at it later, but it should not exists in rsyslog..
removing the /maillog would cause that no mail is sent

[17Halbe]

I had the same error once. But I thought the build process had a hickup.
I just confirmed it. It's a bug.
This is the line where the mail.log logrotate setting should get removed:
https://github.com/tomav/docker-mailserver/blob/2e06228b101b4deff794686e3cb997e458eb3d3b/Dockerfile#L201
That's step 43 during the build process.
The sed command should be following the next line. Basically switch line 201 with 202.