Older Versions of Contao (till 4.3) working like expected with sending emails via sendmail.
After upgrade to Contao 4.9 I got some errors at Providers like 1u1 / ionos or mittwald.
The error in the logs sound like:
"Expected response code 220 but got an empty response"
Sending Mails from CLI of the Server (means if logged in via SSH) working like expected:sendmail test" |
Source: Symfony Questions