An issue was introduced in Domino 9.0.1 FP9 that could result in SMTP mail headers with random characters inserted into From, Sendto, and Copyto fields. This could then result in non-delivery of mail to/from Internet email addresses when using the Domino notes.ini parameter SMTPVerifyAuthenticatedSender=1.
Symptoms of the issue include receiving messages containing garbled sender names. Opening the message and replying results in a number of embedded garbled characters in the header. You can observe this by viewing the page source or by simply examining the content when opening an email. Another method is to capture the SMTP outbound message and examine the header.
This issue is tracked as SPR# JCARAQSJB6 and is fixed in Domino 9.0.1FP9 Interim Fix 1. For download links, go to the Domino tab in technote 1657963 – Interim Fixes & JVM patches for 9.0.1.x versions of IBM Notes/Domino & add-ons.