"Can not write to queue directory" error and other sendmail issues after updating linode from Debian 8 to Stable

Question

I followed this tutorial to upgrade my linode instance from Debian 8 to Stable. In the wake of that upgrade, I've had several errors/issues with sendmail.

1. $ which sendmail doesn't return anything. I do have sendmail installed. It's at /usr/sbin/sendmail.

2. Sendmail's permissions are as follows:

   $ ls -la /usr/sbin/sendmail lrwxrwxrwx 1 root root 26 Jul 17 12:41 /usr/sbin/sendmail -> /etc/alternatives/sendmail

   The link (/etc/alternatives/sendmail) is highlighted in red.

3. When I try to send a test email with sudo echo "Subject: sendmail test" | /usr/sbin/sendmail -v [email protected] I get the following error:

   can not write to queue directory /var/spool/mqueue-client/ (RunAsGid=115, required=0): Permission denied

   That directory's permissions are:

   $ ls -la /var/spool/mqueue-client drwxrwxr-x 2 root root 4096 Sep 15 2018 mqueue-client

So, I obviously have some sort of permission/ownership issue, but I also think there's something else going on given items 1 and 2. I need to be able to receive emails from the system's OSSEC and Fail2ban, so I can't really go without a working email client/server. I'm just not sure how to fix these issues.

My sendmail was simply installed with $ sudo apt-get install sendmail sendmail-bin, so it came direct from Debian's repos, which is why I'm a bit baffled by these issues... I assumed that whatever configuration was needed would be handled by the installation process.

EDIT: the output of ls -l /etc/alternatives/sendmail*

lrwxrwxrwx 1 root root 24 Jul 17 12:41 /etc/alternatives/sendmail -> /usr/lib/sm.bin/sendmail lrwxrwxrwx 1 root root 42 Jul 17 12:41 /etc/alternatives/sendmail.8.gz -> /usr/share/man/man8/sendmail.sendmail.8.gz lrwxrwxrwx 1 root root 24 Jul 17 12:41 /etc/alternatives/sendmail-msp -> /usr/lib/sm.bin/sendmail lrwxrwxrwx 1 root root 42 Jul 17 12:41 /etc/alternatives/sendmail-msp.8.gz -> /usr/share/man/man8/sendmail.sendmail.8.gz lrwxrwxrwx 1 root root 24 Jul 17 12:41 /etc/alternatives/sendmail-mta -> /usr/lib/sm.bin/sendmail lrwxrwxrwx 1 root root 42 Jul 17 12:41 /etc/alternatives/sendmail-mta.8.gz -> /usr/share/man/man8/sendmail.sendmail.8.gz 

Each pair ends in a different color, e.g. /usr/lib/sm.bin/sendmail is highlighted in amber, while /usr/share/man/man8/sendmail.sendmail.8.gz is highlighted in red. It's the same colors - amber and red - for each pair.

EDIT2: The output of (echo subject: test; echo ; echo test) | /usr/sbin/sendmail -d44.4 -i -v username (I used my real username, but have adjusted the resulting output for security):

$ (echo subject: test; echo ; echo test) | /usr/sbin/sendmail -d44.4 -i -v username safefile(/etc/mail/submit.cf, uid=1000, gid=0, flags=6000, mode=400): safedirpath(/etc/mail, uid=1000, gid=0, flags=6000, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 4] OK safefile(/etc/mail/relay-domains, uid=1000, gid=0, flags=6580, mode=400): safedirpath(/etc/mail, uid=1000, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK No such file or directory safefile(/etc/mail/service.switch, uid=1000, gid=115, flags=6480, mode=400): safedirpath(/etc/mail, uid=1000, gid=115, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 4] OK safefile(/etc/mail/service.switch, uid=1000, gid=115, flags=6480, mode=400): safedirpath(/etc/mail, uid=1000, gid=115, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 4] OK safefile( , uid=1000, gid=115, flags=40, mode=660): safedirpath(., uid=1000, gid=115, flags=40, level=0, offset=0): [dir .] OK No such file or directory [final dir . uid 111 mode 42770] Success safedirpath(/var/spool/mqueue-client, uid=1000, gid=115, flags=0, level=0, offset=0): [dir /var/spool/mqueue-client] OK safefile(./dfx6MIGnM5005502, uid=1000, gid=115, flags=2040, mode=600): safedirpath(., uid=1000, gid=115, flags=2040, level=0, offset=0): [dir .] OK No such file or directory [final dir . uid 111 mode 42770] Success username... Connecting to [127.0.0.1] via relay... 220 major-productions.com ESMTP Sendmail 8.15.2/8.15.2/Debian-12; Mon, 22 Jul 2019 14:16:49 -0400; (No UCE/UBE) logging access from: localhost(OK)-localhost [127.0.0.1] >>> EHLO major-productions.com 250-major-productions.com Hello localhost [127.0.0.1], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-EXPN 250-VERB 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-AUTH DIGEST-MD5 CRAM-MD5 250-DELIVERBY 250 HELP >>> VERB 250 2.0.0 Verbose mode >>> MAIL From:<[email protected]> SIZE=20 [email protected] 250 2.1.0 <[email protected]>... Sender ok >>> RCPT To:<[email protected]> >>> DATA 250 2.1.5 <[email protected]>... Recipient ok 354 Enter mail, end with "." on a line by itself >>> . 421 4.3.0 collect: Cannot write ./dfx6MIGnHm005503 (bfcommit, uid=0, gid=115): No such file or directory >>> QUIT username... Deferred: 421 4.3.0 collect: Cannot write ./dfx6MIGnHm005503 (bfcommit, uid=0, gid=115): No such file or directory safefile(/var/lib/sendmail/sm-client.st, uid=1000, gid=115, flags=2282, mode=600): safedirpath(/var/lib/sendmail, uid=1000, gid=115, flags=2282, level=0, offset=0): [dir /var/lib/sendmail] OK No such file or directory safefile(/var/lib/sendmail/sm-client.st, uid=1000, gid=115, flags=2282, mode=600): safedirpath(/var/lib/sendmail, uid=1000, gid=115, flags=2282, level=0, offset=0): [dir /var/lib/sendmail] OK No such file or directory Closing connection to [127.0.0.1] 

EDIT 3: the output of (echo subject: test; echo ; echo test) | /usr/sbin/sendmail -Am -d44.4 -i -v username while logged in as root (with the username obfuscated as before):

# (echo subject: test; echo ; echo test) | /usr/sbin/sendmail -Am -d44.4 -i -v username safefile(/etc/mail/sendmail.cf, uid=0, gid=0, flags=6000, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6000, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 400] OK safefile(/etc/mail/local-host-names, uid=0, gid=0, flags=6580, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 400] OK safefile(/etc/mail/relay-domains, uid=0, gid=0, flags=6580, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK No such file or directory safefile(/etc/mail/service.switch, uid=0, gid=0, flags=6480, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 400] OK safefile(/etc/mail/service.switch, uid=0, gid=0, flags=6480, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 400] OK safedirpath(/var/spool/mqueue, uid=0, gid=0, flags=4, level=0, offset=0): [dir /var/spool/mqueue] OK safefile(/etc/mail/service.switch, uid=0, gid=0, flags=6480, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=6580, level=0, offset=0): [dir /etc/mail] OK [uid 0, nlink 1, stat 100644, mode 400] OK safefile(/etc/mail/aliases.db, uid=0, gid=0, flags=584, mode=400): safedirpath(/etc/mail, uid=0, gid=0, flags=584, level=0, offset=0): [dir /etc/mail] OK [uid 110, nlink 1, stat 100640, mode 400] OK safedirpath(/home/username, uid=1000, gid=1000, flags=1985, level=0, offset=0): [dir /home/username] OK safefile(/home/username/.forward.major-productions, uid=1000, gid=1000, flags=1895, mode=400): No such file or directory safedirpath(/home/username, uid=1000, gid=1000, flags=1985, level=0, offset=0): [dir /home/username] OK safefile(/home/username/.forward, uid=1000, gid=1000, flags=1895, mode=400): No such file or directory safefile(./dfx6MKLN6r006080, uid=0, gid=0, flags=2040, mode=600): safedirpath(., uid=0, gid=0, flags=2040, level=0, offset=0): [dir .] OK No such file or directory [final dir . uid 0 mode 40700] Success username... Connecting to local... safefile(/usr/sbin/sensible-mda, uid=0, gid=0, flags=41904, mode=0): safedirpath(/usr/sbin, uid=0, gid=0, flags=41904, level=0, offset=0): [dir /usr/sbin] OK [uid 0, nlink 1, stat 104755, mode 0] OK username... Sent safefile(/var/lib/sendmail/sendmail.st, uid=0, gid=0, flags=2282, mode=600): safedirpath(/var/lib/sendmail, uid=0, gid=0, flags=2282, level=0, offset=0): [dir /var/lib/sendmail] OK No such file or directory safefile(/var/lib/sendmail/sendmail.st, uid=0, gid=0, flags=2282, mode=600): safedirpath(/var/lib/sendmail, uid=0, gid=0, flags=2282, level=0, offset=0): [dir /var/lib/sendmail] OK No such file or directory 

Answer 1

1. $ which sendmail doesn't return anything.

sendmail IS NOT installed in non privileged users' PATH => you observe expected/normal result. sendmail is expected to be executed by other programs like mail which use full/absolute path.

3. can not write to queue directory /var/spool/mqueue-client/ (RunAsGid=115, required=0): Permission denied

fix /var/spool/mqueue-client permissions and ownership

chown smmsp:smmsp /var/spool/mqueue-client` chmod 02770 /var/spool/mqueue-client` 

MODERN SENDMAIL DOES NOT REQUIRE TO BE SET INSTALLED AS SET ROOT ID

see results of ls -l --dereference /usr/sbin/sendmail in the question's comments:
-r-sr-sr-t 1 root smmsp 860672 Sep 15 2018 /usr/sbin/sendmail

Change permission of the final target of /usr/sbin/sendmail and /etc/alternatives links in Debian:

chmod u-s /usr/lib/sm.bin/sendmail 

Answer 2

Does it work if you run this:

echo "Subject: sendmail test" | sudo sendmail /usr/sbin/sendmail -v [email protected]

The distinction being that you are running echo as root, but not sendmail.

Thus the message: "(RunAsGid=115, required=0): Permission denied"

The "115" is the Group Id of your user, and it is expecting "0" (which is roots)