Hello everyone,
I'm trying to set up a reporting system using Monit, with email alerts forwarded through my Hotmail account. However, the setup isn't working, and I'm receiving the following error:
SMTP: Mailserver response error -- 451 5.7.3 STARTTLS is required to send mail [DX0P273CA0003.AREP273.PROD.OUTLOOK.COM 2026-04-21T17:04:23.671Z 08DE9DD04CF197D8]
STARTTLS is mandatory for authentication, but it seems Monit isn't initiating a TLS connection properly. Has anyone successfully configured Monit to send emails via Hotmail/Outlook.com? If so, could you share the correct SMTP settings or any workarounds?
Mine works with SSL Version set to AUTO
I guess, "Mail Server SSL Connection" doesn't do STARTTLS, it rather just let Monit connect via SSL (usually port 465).
So maybe Monit connects successfully if you remove this check.
Or you can try port 465. Don't know, if Office 365 supports this.
Quote from: lnet.admin on April 22, 2026, 07:52:00 PMMine works with SSL Version set to AUTO
are you using MS email domain? if so could you please share the setting
Quote from: viragomann on April 22, 2026, 11:34:32 PMI guess, "Mail Server SSL Connection" doesn't do STARTTLS, it rather just let Monit connect via SSL (usually port 465).
So maybe Monit connects successfully if you remove this check.
Or you can try port 465. Don't know, if Office 365 supports this.
i have tried that it did not work! im not sure if Monit is design to support such connection, although gmail adopt the same yet it can be connected that what i have seen in youtube!
Yes, I use Monit with SSL on port 465 (SMTPS) with my mail provider and it works.
But most of the big ones only support port 587 with STARTTLS and have on opt-in for SMTPS if at all.
thank you all, i guess this is something to be consider for the next update adopting STARTTLS in Monit