Mail with PHP error after upgrade from 3.X to 4.X

ii  openmediavault                   4.1.4-1                        all          openmediavault - The open network attached storage solution
ii  openmediavault-keyring           1.0                            all          GnuPG archive keys of the OpenMediaVault archive
ii  openmediavault-omvextrasorg      4.1.3                          all          OMV-Extras.org Package Repositories for OpenMediaVault
ii  php-bcmath                       1:7.0+49                       all          Bcmath module for PHP [default]
ii  php-cgi                          1:7.0+49                       all          server-side, HTML-embedded scripting language (CGI binary) (default)
ii  php-common                       1:49                           all          Common files for PHP packages
ii  php-fpm                          1:7.0+49                       all          server-side, HTML-embedded scripting language (FPM-CGI binary) (default)
ii  php-mbstring                     1:7.0+49                       all          MBSTRING module for PHP [default]
ii  php-pam                          1.0.3-1                        amd64        pam module for PHP 7
ii  php-xml                          1:7.0+49                       all          DOM, SimpleXML, WDDX, XML, and XSL module for PHP [default]
rc  php5-cgi                         5.6.33+dfsg-0+deb8u1           amd64        server-side, HTML-embedded scripting language (CGI binary)
ii  php5-cli                         5.6.33+dfsg-0+deb8u1           amd64        command-line interpreter for the php5 scripting language
ii  php5-common                      5.6.33+dfsg-0+deb8u1           amd64        Common files for packages built from the php5 source
ii  php5-fpm                         5.6.33+dfsg-0+deb8u1           amd64        server-side, HTML-embedded scripting language (FPM-CGI binary)
ii  php5-json                        1.3.6-1                        amd64        JSON module for php5
rc  php5-pam                         1.0.3-4                        amd64        pam module for PHP 5
rc  php5-proctitle                   0.1.2-2                        amd64        proctitle module for PHP 5
ii  php7.0-bcmath                    7.0.27-0+deb9u1                amd64        Bcmath module for PHP
ii  php7.0-cgi                       7.0.27-0+deb9u1                amd64        server-side, HTML-embedded scripting language (CGI binary)
ii  php7.0-cli                       7.0.27-0+deb9u1                amd64        command-line interpreter for the PHP scripting language
ii  php7.0-common                    7.0.27-0+deb9u1                amd64        documentation, examples and common module for PHP
ii  php7.0-fpm                       7.0.27-0+deb9u1                amd64        server-side, HTML-embedded scripting language (FPM-CGI binary)
ii  php7.0-json                      7.0.27-0+deb9u1                amd64        JSON module for PHP
ii  php7.0-mbstring                  7.0.27-0+deb9u1                amd64        MBSTRING module for PHP
ii  php7.0-opcache                   7.0.27-0+deb9u1                amd64        Zend OpCache module for PHP
ii  php7.0-readline                  7.0.27-0+deb9u1                amd64        readline module for PHP
ii  php7.0-xml                       7.0.27-0+deb9u1                amd64        DOM, SimpleXML, WDDX, XML, and XSL module for PHP