I am using Thunderbird 45.8.0 (current) on Win-10.

There are 2 different calendars on 2 separate accounts on the same server (provider: 2 free mail & calendar acocunts on web.de), which a friend and I would like to share and incorporate in Thunderbird. Simple "merging" into one calendar is not an option, since we both share this calendar also with other (not completely overlapping) people.

Incorporating either calendar works nicely, but the second one does not work in parallel (no matter which is first/second; error: the calendar entry is shown, but pale and not working, when clicking properties - "switch this calendar on", this does not cheange the status).

To me, it seems that the problem might be (I am not sure), that Thunderbird cannot distinguish the 2 calendars because they are on the same provider, address ist: https://kalender.web.de/begenda/dav/username@web.de/calendar (as per help on https://hilfe.web.de/kalender/synchronisieren/thunderbird.html).

I found and tried the following suggestions (https://sys4.de/en/blog/2014/07/11/multiple-caldav-calendars-thunderbird-lightning-auth-problem/):

  1. "Adding 'username@' before the URL should also work, e.g. http(s)://username@myserver/owncloud/..." -> does not work (address not accepted, same with username:password@...) (might I need to place username:password somewhere els in this address (tried, but did not help so gfar)
  2. set calendar.network.multirealm to TRUE -> still does not work.

In Thunderbird password manager, the two (different) usernames and (different) passwords for the zwo calendars are correctly included (and work if either calendar is used separately).

Is there any solution to handle 2 calendars on the same provider/server? We would prefer

  • stay on the same existing providers if possible, otherwise
  • a solution that does not simply rely on using different providers for each calendar, since we might become more people/calendars and there is a limited number of trusted providers.

Update 2017-03-12: I found these two bug reports. They are quite old, but seem to be difficult (13 years!) and still unsolved - I'd be happy if someone could disprove this or come up with a workaround...

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This is a wild idea and I don't know if it will work, but I have no way of testing.

If, as you suspect, the problem is the same server-name being used twice, there is a simple way to give the server a second and different name:

  1. Use ping kalender.web.de to get the IP address of the server, giving for example 123.456.789.012
  2. Edit the hosts file so as to invent an alias to the same server by adding a line such as:
    myalias.com 123.456.789.012
  3. Use for one of the accounts the name of https://myalias.com/begenda/dav/username@web.de/calendar thus directing that dummy server-name to the same IP address.
  4. Edit the Apache and Davical configs to support the new domain.

This might work on condition that using identical website names is really the problem, and if Thunderbird is not smart enough to detect that the same site is now referenced twice.

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  • So this worked -- with the caveat that if you're using https on the server, it throws a SSL_ERROR_BAD_CERT_DOMAIN error (since the SSL certificate subject is the "main" domain). Fortunately Thunderbird/Firefox allow you to add a security exception for the domain, which works around this reasonably well. – Doktor J Sep 13 '17 at 2:09
  • Of course if you own your own domain and run your own server, you can add a new subdomain at will, and then configure CalDAV and Apache to handle it. You'll need a cert to go with the new domain too, but with www.letsencrypt.org and other free certs, that's less of a concern. – Doktor J Sep 13 '17 at 2:13
  • Glad you managed to get it working. You could also submit a bug report for the problem. – harrymc Sep 13 '17 at 6:00

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