The Appointments function does not work well in the Calendar App


when i try to book an appointment like anyone post using the public link. sends an error:

“Could not book the appointment. Please try again later or contact the organizer.”

could you help me?


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The calendar application does not work well.

please help.

when an appointment is executed.

Note: I am not referring to the dating app.

I have the same issue, and the exact same error message.

Nextcloud version (eg, 20.0.5): 23.0.5
Operating system and version (eg, Ubuntu 20.04): Ubuntu Server 20.04
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4.29
PHP version (eg, 7.4): 7.4.29

The issue you are facing:
I receive the error message “Could not book the appointment. Please try again later or contact the organizer.” when attempting to book an appointment using the calendar appointment function.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:
I click on the user’s profile, click on the icon for appointments under the user’s avatar, I click on a time slot, it auto fills my name and email, I click on Book The Appointment button, then the error appears.

The output of your Nextcloud log in Admin > Logging:

[calendar] Error: Could not send mail: Expected response code 354 but got code "554", with message "554 5.5.1 Error: no valid recipients

POST /nextcloud/index.php/apps/calendar/appointment/1/book
from by mike at 2022-06-09T18:17:50+00:00

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):


The output of your Apache/nginx/system log in /var/log/____:



Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.


I disabled the other Appointment app thinking they may be conflicting, however the error persists.

I tried different emails, names, time slots, etc. All fail.

I’m not even sure what to provide as additional information for this app. The error message is vague.