Solution for Unsupported sendmail command flags [/usr/sbin/sendmail]. Must be one of "-bs" or "-t" but can include additional flags.

Typo3phpsendmail.md

In Typo3 8.7 geht bei mir der phpsendmail nicht mehr. Die Fehlermeldung sieht so oder aehnlich aus.

Core: Exception handler (WEB): Uncaught TYPO3 Exception: Unsupported sendmail command flags [/usr/sbin/sendmail]. Must be one of "-bs" or "-t" but can include additional flags. | Swift_TransportException thrown in file /opt/typo3_src-8.7.16/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/SendmailTransport.php in line 146. Requested URL: http://typosux.de/typo3/install.php?&install[action]=testSetup&install[controller]=tool&install[context]=backend 

Wenn man die Mails ueber smtp verschickt, dann geht es aber.

$GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport'] = 'smtp';
$GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_password'] = 'xxx';
$GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_server'] = 'smtp.domain.org:25';
$GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_username'] = 'username';
$GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_smtp_port'] = '25';

http://www.typo3forum.net/discussion/77831/powermail-nicht-mit-phpsendmail-sondern-ueber-smtp-senden