Invitation: Only the first three email addresses are used for sending but about 20 are added to the list #6195
Description
With a docker installation of BBB and thus using version 3.6.3 of greenlight, when inviting a bunch of people by email address to a site customized to use the registration method "Join by invitation", only the first three addresses are used for sending an email, but about twenty of them are afterwards listed on the "Manage Users" admin page on the "Invited" list.
The number of only three has been verified in using four addresses but 20 for the list of emailaddresses used in the "Invited" list is only a guess, because we have not verified it. We have used more than 20 addresses but don't know exactly how many of them afterwards appeared on the list.
From a quick look into the log files, it seems like the mail server has rejected the delivery with "too many connections" but in retrospect, I can no longer tell from the log which addresses were used, so I can't say what the critical number is, but I would guess 3.
As a consequence if the mailer uses a new connection for every mail sent, there should be a waiting time between these jobs or the number of accepted emails for one invitation call should be restricted.
However, all failed jobs must be marked as such and must not added to the list. And all addresses from the form must be used or an error message like "too many addresses, use a max of 5" must be shown.