🎫 Ticket: AxiosError: Request failed with status code 400

Hello,

I’m currently experiencing an issue sending emails from our Nextcloud instance (VM-NEXTCLOUD) to our Exchange server

:wrench: Tests performed:

  • Ports 25, 465, and 587 are open (verified with telnet and nc).
  • Ping and DNS resolution work as expected.
  • The Exchange server responds properly via telnet on port 25 and accepts SMTP commands such as HELO, MAIL FROM, RCPT TO without authentication.
  • However, when using SMTP from Nextcloud, no emails are sent — whether using authentication or not, STARTTLS or SSL.

:red_exclamation_mark: Observation:

The Exchange server accepts manual SMTP connections, but refuses or blocks connections initiated by Nextcloud, even with the correct credentials and encryption.