This can be done through either the webUI (Settings, Basic settings, Email server) or by editing config.php and adding:
'mail_smtpmode' => 'smtp',
'mail_sendmailmode' => 'smtp',
'mail_from_address' => 'example', # [email protected]
'mail_domain' => 'domain.tld', # [email protected]
'mail_smtphost' => '192.168.1.2', # IP of gotify-server
'mail_smtpport' => '1025', # make sure this port is mapped if using gotify on docker
'mail_smtpauth' => 1,
'mail_smtpname' => 'admin', # gotify username to send email to
'mail_smtppassword' => '', #leave blank
'mail_smtpauthtype' => 'PLAIN',
WIP