javax.email.internet error with invalid characters in email address

The corresponding application message of the queue NOTIFICATION errors out with the following error when the recepient email address contains control characters (Ex : web­mas­ter@​minimax.​de) or umlauts (Ex: web­mas­ter@kältetechnik.​de). 

Error while sending data… Caused by : javax.mail.internet.AddressException: Domain contains control or whitespaces

However, lot of our customers have umlauts in their email addresses, and it’s not clear which javax package IFS users within the framework for email sending, and supports which RFC versions.

(Ex: is it javax.mail:mail  or com.sun.mail:javax.mail , etc)

Do we have a pre-defined set of characters which should be escaped (marked as invalid for use within IFS emails) or if there’s knows control character limitation (or double-byte character limitation)?