A particular user is not receiving JIRA notifications: such as mentioning in a comment; when the user is reporter/assignee etc.
The email address is valid as other non-JIRA emails are being received. I have tried sending the user a test email from JIRA (configure mail) and the error below was prompted:
550 User not found
DEBUG SMTP: Invalid Addresses
DEBUG SMTP: <user's email address>
DEBUG SMTP: Sending failed because of invalid destination addresses
DEBUG SMTP: MessagingException while sending, THROW:
javax.mail.SendFailedException: Invalid Addresses;
nested exception is:
com.sun.mail.smtp.SMTPAddressFailedException: 550 User not found