I've installed ssmtp and then edited the ssmtp.conf file so could try sending a mail but says cannot open mail:25 however in the conf file I set it to gmail port 467 and I am pretty sure everything else is right.

What specifically do I need to look for with this error or could it be any number of settings in and outside of the configuration file?

# /etc/ssmtp.conf -- a config file for sSMTP sendmail.
# See the ssmtp.conf(5) man page for a more verbose explanation of the
# available options.

# The person who gets all mail for userids < 500
# Make this empty to disable rewriting.

# The place where the mail goes. The actual machine name is required
# no MX records are consulted. Commonly mailhosts are named mail.domain.com
# The example will fit if you are in domain.com and your mailhub is so named.

# Example for SMTP port number 2525
# Example for SMTP port number 25 (Standard/RFC)
# mailhub=mail.your.domain
# Example for SSL encrypted connection
# mailhub=mail.your.domain:465

# Where will the mail seem to come from?

# The full hostname

# Set this to never rewrite the "From:" line (unless not given) and to
# use that address in the "from line" of the envelope.

# Use SSL/TLS to send secure messages to server.

# Use SSL/TLS certificate to authenticate against smtp host.

# Use this RSA certificate.

# Get enhanced (*really* enhanced) debugging information in the logs
# If you want to have debugging of the config file parsing, move this option
# to the top of the config file and uncomment

Interestingly all the files in /etc/pki/tls/certs/ are the exact same ones I deleted in my /etc/ssl folder! haha Now I know a certain amount of business happened when creating an untrusted cert.

  • Does your firewall blocks the port 25
    – Nidal
    Jun 7 '14 at 14:17
  • I don't know, is that the only possibility?
    – cea
    Jun 7 '14 at 14:30
  • 2
    Seeing the complete configuration file would help to solve the issue. Jun 7 '14 at 15:18
  • 1
    @cea: once again (as in the Apache + ssl.conf) question you give too little information. The error message indicates it's trying to contact a host named mail on port 25. Does the name mail resolve (use host, nslookup or getent hosts mail to verify)? Coincidentally mailhub=mail is the default setting in the config file. It would also be good to know what you expect to achieve by connecting to port 467 with "gmail" (which host????). On another note: have you tried nullmailer? Jun 7 '14 at 15:20
  • 1
    ssmtp does NOT verify the SSL/TLS certificate of the remote server on the current debian, ubuntu and redhat releases and also does NOT verify the hostname of the certificate. This is a major issue, as this effectively renders the encryption useless and your password is being transmitted alike to being plaintext and anyone can sniff it. ssmtp has had no active development since atleast 2009. So, if you care about the security of the email account you use for your servers outgoing emails, do NOT use ssmtp, but postfix (or something else) instead: unix.stackexchange.com/a/118101/72087
    – Zulakis
    Feb 24 '16 at 10:42
ssmtp: Cannot open mail:25 

can be caused by file permission errors on /etc/ssmtp/ssmtp.conf. Whatever application is trying to run ssmtp cannot read the file.

chmod 640 /etc/ssmtp/ssmtp.conf
chown root:mail /etc/ssmtp/ssmtp.conf

& add the application sending email to the mail group (e.g logcheck if it is not part of adm group)

For completeness your smtp.conf should look something like:

#mailhub=gmail.com:587 ### -> note 587 for STARTTLS
#UseSTARTTLS=Yes ### => gmail needs this (not all servers do)

# on Fedora / Red Hat / or with ssmtp-validate-TLS-server-cert.patch

The first uncommented mailhub=mail would seem to be the cause for this.

Without an FQDN and a port number, I imagine it configures ssmtp to attempt to connect on port 25 to a host called mail in your default domain (however you have that set up locally) which presumably does not exist.

  • @RuiFRibeiro Thanks for the feedback; updated with a brief explanation.
    – tripleee
    May 23 '17 at 4:36

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