Option to force users to change password at first login
The standard procedure for me is to create the account, put in a junk password.
Then in Portal members menu you can 'reset password' for that user and it provides a randomized 8-character temporary password.
I then send a boilerplate email to the user providing a link to the Portal login and their username and temporary password to login for the first time.
Using this method, they are forced to create their own unique password (and security question).
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THAT SAID, I completely agree that Portal should make this process basically native so that as an admin you don't have to go through this 'external' hoop of sending an email manually to a user, which is a big pain if you are adding a lot of users at once. Portal ought to be able to send an invite via email with a link to create a unique password for their account, similar to AGOL.
I am not sure if the options exist/change if you add an Email configuration in Portal > Settings > Security > Email settings. I don't have that set up in my configuration currently but maybe someone else can confirm if this changes anything when email account is setup with Portal for notifications.
Update:
I added a test smtp email account to add to my Portal (11.1 in my case) to see what may change. The behavior DOES change in at least 1 way. Although creation of a new account still requires you to enter a password, when performing the password reset step I mentioned above, as the Admin, you no longer see the popup with temporary password information when resetting a user password.
Instead, the user is directly sent a boilerplate email with login instructions with the temporary password:
I searched around in the Portal Settings but I don't see where this boilerplate email can be customized. In my case, I'm not sure that this is good enough since my users sometimes are being onboarded to our org and have no idea what GIS is and maybe have never even used web maps much. I try to put in some extra information in my emails to new users to give more context to why they are receiving this and what this account is to be used for. For example, we use Portal user store as our single sign-on for Cityworks. I add important context that this account is what is used for Cityworks login, or other secured GIS resources, etc. I often customize the boilerplate email a little bit if I know the user has particular use cases.
It appears an idea for customized emails for AGOL has been open for many years and it doesn't seem to have any official response. So I assume Portal is in the same boat.
https://community.esri.com/t5/arcgis-online-ideas/customizing-arcgis-online-administrative-and/idi-p...