Question

I have run into an issue this weekend with case sensitivity of headers in MailSendingMessageHandler. Are mail headers expected to be case sensitive in SI? A brief bit of research has led to me to discover that email headers in general should be insensitive (1).

Is this an oversight in SI or have I missed something obvious?

1. Are email headers case sensitive?

Answer 1

The RFCs are talking about the headers that go over the wire (e.g. SMTP). The MailSendingMessageHandler receives a Spring Integration (SI) message and maps the SI headers to SMTP headers.

SI headers are case-sensitive.

For this reason (among others), we recommend using framework constants for the headers, instead of coding your own values.

For example

MailHeaders.FROM

in java or

#{T(org.springframework.integration.mail.MailHeaders).FROM}

in a SpEL expression specifying the header name.