Send E-Mail to all "unsent invitations"

[martinbu]

This is part 1/3 of the issue #1268

Is your feature request related to a problem? Please describe. It is not possible to invite all not yet invited shares (unsent invitations). I have contact groups with a lot of contacts. With the #902 I can now search for them and add them to the pool. But with the current implementation I have to first click on resolve to individual shares and then invite every contact individually.

Describe the solution you'd like A Button to send an invocation email to all shares which are not invited via email yet