Kimai uses the Symfony Mailer component for sending emails. Please read their documentation to find out more about possible connection details.
You have to adapt two settings in your
.env configuration file:
MAILER_URL- the connection details for sending emails
MAILER_FROM- an application wide “from” address for all emails
You can test your email configuration by registering a new account or using the password reset function.
If your SMTP credentials contain special character like
@ or other ones which are not URL-safe, then they need to be urlencoded.
This can be done with one command, assuming your password is
mG0/d1@3aT.Z)s then execute:
php -r "echo urlencode('mG0/d1@3aT.Z)s');" mG0%2Fd1%403aT.Z%29s
MAILER_URL might look like this:
If you have the following error in your logfile:
app.ERROR: Exception occurred while flushing email queue: Expected response code 354 but got code "503", with message "503-All RCPT commands were rejected with this error: 503-R1: HELO should be a FQDN or address literal (See RFC 2821 18.104.22.168) 503 Valid RCPT command must precede DATA "  
you might suffer from a wrong configuration (read the documentation linked above) and try a full featured SMTP URL with a dedicated user account for authentication:
Password should not contain URL characters like ‘&@:’, which can cause problems parsing the SMTP URL (see above).