THE PROBLEM

Bug Part 1

Email addresses of format 'andré@blah.com' cannot be used with registered Jira users, validation on entry fails.

Bug Part 2

Email addresses of format 'andré@blah.com' fails:

InternetAddress ia=new InternetAddress("andré@blah.com");

Upgrading javamail will enable a wider range of customers to interact with JIRA.

THE SOLUTION

Jira 7.9.x still ships with Javamail v1.5.6, Javamail v1.6.0 specifically adds "Support for internationalized email addresses (RFC 6530/6531/6532)"

• https://javaee.groups.io/g/javamail/message/1

CONTEXT

Gmail has support RFC6530 since 2014.

• https://www.zdnet.com/article/gmail-to-support-accented-and-non-latin-characters 

@note to Atlassian.  Yes, users won't ever see this or vote for it, that doesn't mean its not critical and something you should just 'not fix'...