How to verify the reason, why the company’s SMTP email doesnt works with you app (Linux Ubuntu)?

Install SMTP sender tool:

sudo apt-get install sendemail

Try to send an email:

sendemail -f [email protected] -t [email protected] -u "Email subject" -m " Test email message" -s -o tls=no

Check and solve the logs (and errors):

sendemail[487]: ERROR => TLS setup failed: SSL connect attempt failed error:0A000086:SSL routines::certificate verify failed

More details:

sendemail-1.56 by Brandon Zehm <[email protected]>

Synopsis:  sendemail -f ADDRESS [options]

    -f ADDRESS                from (sender) email address
    * At least one recipient required via -t, -cc, or -bcc
    * Message body required via -m, STDIN, or -o message-file=FILE

    -t ADDRESS [ADDR ...]     to email address(es)
    -u SUBJECT                message subject
    -m MESSAGE                message body
    -s SERVER[:PORT]          smtp mail relay, default is localhost:25
    -S [SENDMAIL_PATH]        use local sendmail utility (default: /usr/bin/sendmail) instead of network MTA

    -a   FILE [FILE ...]      file attachment(s)
    -cc  ADDRESS [ADDR ...]   cc  email address(es)
    -bcc ADDRESS [ADDR ...]   bcc email address(es)
    -xu  USERNAME             username for SMTP authentication
    -xp  PASSWORD             password for SMTP authentication

    -b BINDADDR[:PORT]        local host bind address
    -l LOGFILE                log to the specified file
    -v                        verbosity, use multiple times for greater effect
    -q                        be quiet (i.e. no STDOUT output)
    -o NAME=VALUE             advanced options, for details try: --help misc
        -o message-content-type=<auto|text|html>
        -o message-file=FILE         -o message-format=raw
        -o message-header=HEADER     -o message-charset=CHARSET
        -o reply-to=ADDRESS          -o timeout=SECONDS
        -o username=USERNAME         -o password=PASSWORD
        -o tls=<auto|yes|no>         -o fqdn=FQDN

    --help                    the helpful overview you're reading now
    --help addressing         explain addressing and related options
    --help message            explain message body input and related options
    --help networking         explain -s, -b, etc
    --help output             explain logging and other output options
    --help misc               explain -o options, TLS, SMTP auth, and more