I'm working on a project which relies on having unique groups for each site. I've experienced some issues when inviting external users to these groups via the "Share this site" feature. Invites fail at random (around 50% of the time) -when trying to send the invites an error dialog is shown saying that there's something wrong with the invite feature and the invites can't be sent.
I've been told (by support staff on the office365 forums) that you should only invite users to the default SITE COLLECTION-level groups (the groups called members and visitors). apparently the features that handle external users rely on them being in these groups. According to my tests, it seems like it might be true: I never get errors when inviting to SiteCollection-level groups, but I sometimes get errors when inviting to site-level groups. So weird that something like that random errors (rather than consistent errors..)
A) Is this true?
B) If it is true, how are you supposed to handle groups? Say you are on siteX and invite a user to the siteCollection-level Members group. Then you also want that user to join the members group on siteX. is it possible to add an event reciever that detects when the user joins the siteCollection-level groups, so that he is automatically copied to the members group on siteX?