PHP - 553 Relay banned by Zoho and MyBB mail

Question

I am trying to use Zoho SMTP servers to send registration emails from a MyBB installation. However, emails are never sent, and when I check the logs, I notice that there is an error.

Month Day Year:Hour:Minute host=smtp.zoho.com tls=on auth=on user=user[at]mydomain.com from=user[at]mydomain.com recipients=some.user[at]gmail.com smtpstatus=553 smtpmsg='553 Relaying disallowed' errormsg='the server did not accept the mail' exitcode=EX_UNAVAILABLE

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This is the path of the sendmail path in php.ini

sendmail_path = "/usr/bin/msmtp -C /etc/msmtp/myserver --logfile /var/log/msmtp/myserver.log -a default -t"

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This is the myserver configuration for MSMTP

# Define here some setting that can be useful for every account
defaults
    logfile /var/log/msmtp/general.log

# Settings for default account
account default
    protocol smtp
    host smtp.zoho.com
    tls on
    tls_starttls off
    tls_certcheck off
    port 465
    auth plain
    user user[at]mydomain.com
    password **********
    from user[at]mydomain.com
    logfile /var/log/msmtp/myserver.log

# If you don't use any "-a" parameter in your command line,
# the default account "default" will be used.
# account default: default # (disabled because this gives a "redefined" error)

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The problem is that I know that it works, and that none of the ports are blocked, because when I use the same command on the command line. Email successfully sent and received.

sudo echo -e "Subject: Test Mail\r\n\r\nThis is a test mail" | msmtp --debug -a default --from=user[at]mydomain.com -t some.user[at]gmail.com --file=/etc/msmtp/myserver

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This means that it is either wrong that MyBB is sending emails, or something is wrong with my configuration or the PHP command line that I installed in the php.ini file.

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Answer 1

MyBB, PHP, -f mail(), sendmail. , 5- ( , , 4-)

mail('[e-mail]', 'the subject', 'the message', null,
'[e-mail]');