Mail Handler doesn't add "Created via e-mail received from" when default reporter has capital letters in username

Summary

When an issue is created via email and the email address is not associated to any users in JIRA, the default reporter is used. There will be the following line added to the description of the ticket

[Created via e-mail received from: testing jira <test@example.com>]

If the username of the default reporter has a capital letter in it, the line above will not be added to the description

Steps to Reproduce

1. Create a Mail Server and Mail Handler
2. Create a user with the username Admin
3. Set up a Mail Handler specifying Admin as the default reporter
4. Create an issue via email, making sure that the email used is not associated to any users in JIRA

Expected Results

1. The line [Created via e-mail received from: testing jira <test@example.com>] should be added in the description of the ticket

Actual Results

1. Nothing is added to the description of the ticket

Notes

1. Tested with Admin and aDmin
2. When the username is admin, the line is added as expected

Workaround

1. No workaround. Make sure that the username does not contain capital letters