Horde Kronolith event invitations SMTP configuration


Well-Known Member
Aug 10, 2002
cPanel Access Level
Root Administrator
Horde is pretty confusing to begin with.

When using Kronolith (Calendar) to send out event invitations, Kronolith doesn't use the information in /usr/local/cpanel/base/horde/config/conf.php to send out mail.

Instead it tries to connect to on port 25 and send out unauthenticated mails.

It does not attempt to use SMTP Authentication.

If you have /usr/local/cpanel/base/horde/config/conf.php set to use port 587 for sending out mail, it does not use that.

Steps to reproduce

Log into Horde Webmail account

Select New Event from Calendar

Add some email addresses in the Attendees tab


Send updates to attendees? Select Yes

There was an error sending an event notification to [email protected]: Failed to set sender: [email protected] [SMTP: Failed to write to socket: not connected (code: -1, response: )]

Sending mail out through the Mail application in Horde works fine and as expected (through port 587 using the logged in credentials for SMTP Auth). But Kronolith - and perhaps other Horde Applications, do not.

There's a really old discussion about this on the Horde Mailing List:


It's from 2013. Seems to explain the issue I'm facing. But the discussion just seems to end without a resolution.
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