The Redmine registration procedure is a bit fragile: If account activation mail doesn't arrive, we don't know how to make Redmine resend it.
This could happen for several reasons:When that happens, people can still create accounts but the account cannot be activated by them.
However it's still possible for Redmine Administrators to manually activate the account(s).
We don't need to check the person's name as it's not checked by Redmine. Ideally we'd like to have a free form for the (real) name and also make it optional but we didn't find how to do it in a way that is easy to maintain in Redmine.
If you have the mail in Maildir format you can check the DKIM signatures with the following command:
$ cat ./the_mail_in_Maildir_format | dkimverify signature ok
And with claws mail, you can do it by opening the mail, then clicking on "File->Save Email as", and then you can verify it with the same command:
$ cat saved_mail | dkimverify signature ok
Then to activate the account manually in Redmine, you can go in Administration->Users and Select All in Status, and search for the mail address.
Make sure that there is only one email matching, and then, once the user is selected, you should see the following links on the top-right of the page:
Emails Activate Delete Users
You can then activate the account by clicking on "Activate".
Be aware that there is no confirmation and that once the button is clicked, the account is activated immediately.