Jira sends email to username

[Erik Lorentzson]

We have users who have email-like user names that are in fact not valid email addresses. When JIRA sends notifications to them it sends an email to both their registered email address and to their user name. The mail to the user name will always bounce, is there any way to stop JIRA from doing this?

e.g:

Username: invalid@somedomain.com

Email: valid@somedomain.com

JIRA will send emails to both and the first one will always bounce.

[Deleted user]

What Notifications are being sent? Native JIRA Notifications? Custom Emails?

[Erik Lorentzson]

Native notifications (e.g. "new comment on issue" or "issue created")

[Deleted user]

Can you prove that the user's username is not on any other account's "email address"? I have not encountered this before. I got around 20,000~ accounts and this has never happened to me before. 

[Erik Lorentzson]

Searching in the "User Name Contains" field for "invalid@somedomain.com" finds one user, searching for the same in "Email Contains" gives no hits.

Among your accounts do you have any user names that look like emails (but are in fact not valid email addresses)?