Monit and STARTTLS Issue

[Blackdragon83]

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?

[lnet.admin]

Mine works with SSL Version set to AUTO

[viragomann]

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.

[Blackdragon83]

Mine works with SSL Version set to AUTO

are you using MS email domain? if so could you please share the setting

[Blackdragon83]

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.

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!