<On Sat, Feb 14, 2026 at 06:15:26PM +0000, Nuno Silva via Mutt-users wrote:>
> On 2026-02-09, Matthias Apitz wrote: > > > Hello, > > > > I'm adding to all my mails sent with mutt (like this one) two X-header > > lines: > > > > X-Operating-System: FreeBSD 14.0-CURRENT r1400094 (amd64) > > X-message-flag: Mails in HTML will not be read! Please, only plain text. > > > > I got informed by an reader of a mailing-list that my mails get flagged > > in his OutLook mailbox with a small red flag. Technically this is added > > by a Microsoft SPAM protection which adds into my mail a header among other > > stuff a line like this: > > > > ``` > > X-Microsoft-Antispam-Mailbox-Delivery: > > > > ucf:0;jmr:0;auth:0;dest:I;ENG:(910005)(944506478)(944626604)(4710137)(4713098)(499 > > 9163)(920097)(930201)(20251009147)(140003); > > ``` > > > > I did tests with an OutLook destination I've access to and the "culprit" > > seems to be only this X-header: > > > > X-message-flag: Mails in HTML will not be read! Please, only plain text. > > > > Any comments on what could he do or what could I do? > > > > Thanks > > > > matthias > > Are you sure the red flag is related to spam/junk detection and isn't > just Outlook's way of showing that a message has been "flagged", with > the presence of the header being regarded as a flag too? > > I just tested with a Microsoft-hosted account here, and > > 1) I can confirm the flag text still shows up, above the message, in the > current version of Outlook webmail (the blue envelope one). > > 2) Messages with X-Message-Flag get that red flag set. Tooltip over it > says "Unflag this message", and when displaying the message, it also > gets a red flag between headers and body, followed by the red text > "Flagged". > > 3) Both test messages arrived in the Inbox, not "Junk Email". > > -- > Nuno Silva A far as I remeber this is just an annoyer for Outlook users. I have this on my .muttrc since 20+ years. # Outlook Annoyer: Flags and tags each email fairly obviously my_hdr X-Message-Flag: Cranky? Try Free Software instead! It is funny that it is still working. I was used to be asked by outlook users why all my emails are flagged with a small red flag... But this has nothing to do with a spam tag. Best, Nicola
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