SubjectLine
Corex\Mail\SubjectLine · class · Core layer
A subject as an email carries it: plain text, on one line. A subject is a header, not markup. Cleaned as the text of an HTML form it reached a customer changed: “Price <500 EGP” as “Price <500 EGP”, “Sam sam@example.com asked” as “Sam asked”, “Save 50%de today” as “Save 50 today”. So what was typed is kept as typed, and whoever prints a subject into markup escapes it there. What a header cannot hold is a line break: whatever followed one would be read as a header of its own. A break, or any other control character, becomes a space.