Is there any way to have RT use some kind of "reply above this line" email delimiter?

To give myself an answer:
After setting some debug marks one has to state: Incoming mail is processed for the cut line before decryption.
Very pity!

[7001] [Wed Feb 21 13:11:02 2024] [debug]: ... in sub ProcessEntity (/opt/rt5/local/plugins/RT-Extension-EmailReplyDelimiter/lib/RT/Extension/EmailReplyDelimiter.pm:161)
[7001] [Wed Feb 21 13:11:02 2024] [debug]: EffectiveType: application/pkcs7-mime (/opt/rt5/local/plugins/RT-Extension-EmailReplyDelimiter/lib/RT/Extension/EmailReplyDelimiter.pm:166)
[7001] [Wed Feb 21 13:11:02 2024] [debug]: Depth: 1 (/opt/rt5/local/plugins/RT-Extension-EmailReplyDelimiter/lib/RT/Extension/EmailReplyDelimiter.pm:173)
[7001] [Wed Feb 21 13:11:02 2024] [debug]: Message encrypted for user@example.com (/opt/rt5/sbin/../lib/RT/Crypt/SMIME.pm:691)

I don’t know if there is a possible hook location for manipulating the mail content after decryption. But maybe there is the possibility to manipulate the view? One could just reduce the Body of each transaction shown from the beginning to the first occurence of a member of $EmailReplyDelimiters.

Confirmed, it hooks in before any decryption. I didn’t see an easy way to get at the message after that.

I would worry about the overhead of parsing every displayed transaction if processing on view.

Maybe an “On transaction” scrip could do it? It feels like it would be wrong to have a scrip manipulating the content of a transaction after it’s already been stored.

I just meant to reduce the amount of text shown in an transaction view in the sense of

sed '/PATTERN/q' transaction_body

.

This way the original content stays in the DB without disturbing the reader with redundant sections.
The history tab than shows the complete contents anyways.