Hi Jennifer,
Thanks for reaching out.
You can check if Rackspace supports plus aliases by sending an email to [email protected] from any email client. Plus Aliases support is provided by the end mailbox system, not by the sending (SMTP) system.
That said, I have been able to replicate the issue with the SMTP tester and will release a fix today.
Thanks for bringing it up!
Cheers,
Vinny
