Stalwart refuses a VacationResponse subject of 512 bytes or more and a
text or HTML body of 2048 bytes or more, answering only "Field could
not be set." The limit counts bytes, so 1030 "ä" already exceed it,
and the HTML from the rich-text editor reaches it quickly. The save
failed with a generic error.
On Stalwart the vacation settings now check the subject and the text
and HTML that would be sent, and name the limit instead of saving.
Linus Rath
f3aec163c0