Zimbra has this nice feature to share calendars, you share a calendar with a group of people and they get a mail
The following share has been created:
Now when you read that mail in the Zimbra interface .. everything works fine.. there is another mime part with some XML info that Zimbra learns to create an Accept button from.
However lots of people use IMAP or POP3 rather than the webinterface to read their mail.
Non Zimbra clients don't parse that extra XML part, so they get a mail stating that a new share has been created but they never actually see that calendar in their webinterface.
The person who sent the invite also doesn't have an option to resend the invite it seems.
Luckily the receiver can resend the mail to his inbox and then the xml part gets parsed.
Ideally someone not using the webinterface could get a link to click on .
Anyway .. at least it works.. unlike some other groupware solutions.
UPDATE:
Ah the lovely ways of a community support.
Seems like my sender didn't look good enough .. there indeed is a resend function.
And it seems that in the upcoming 5 release the nodes provide you with an URL and a (cleartext) username and password combo