Resolved -
We're not seeing any further reports about this issue and the application is running normally.
Jul 18, 20:38 PDT
Monitoring -
A fix has been released and transactional emails, containing attachments, should be sending successfully via SMTP. Our engineers will continue to monitor the issue.
Jul 18, 20:00 PDT
Identified -
Our engineers have identified an issue which has affected a small number of transactional emails sent via SMTP, containing an attachment. A fix for this is already being worked on and will be released very shortly.
Jul 18, 19:48 PDT