I am a bit confused by this request. With Service Desk, users that exist only in the customer role do not have access to the main Jira site. Instead they only have access to the customer portal. This customer portal won't let them search for other issues, browse other projects, create projects, or anything of the sort. They can only see their own issues, or issues that have been shared with their organization, or issue where they have been added as a requested participant (all of which have to exist in Service Desk projects). In most cases you don't want to grant your customers application access to Jira Core/Software or as a JSD Agent. Users in those roles do have access to the main Jira site and much more ability to search projects, etc.
This customer portal view is rather limited in comparison to the Jira main login site that is used by other licensed Jira users such as JSD Agents or Jira Software/Core users.
Service Desk was not really intended to be an email only channel. There is an existing feature request to do this in https://jira.atlassian.com/browse/JSDSERVER-1012
However with the current versions of Service Desk, I do not believe there is a way in order for your grant these users email access, but then deny them access to the customer portal itself. Please let me know if perhaps the use of the customer portal only might be helpful in your use case here or if you have any additional questions.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.