Thanks Ed. In case someone else is interested in setting this up too, here is where I am so far.
Having the messages in the maildir format on my side, I regularly (upon new message arrival using Mutt's $new_mail_command, and also once a day) scan the To-do folder with a script (here is a simplified version; uses procmail and mblaze packages): #!/bin/zsh while IFS=$'\n' read -r mailfile; do _due=$(formail -c -f -z -x 'Subject' < "${mailfile}" \ | grep --only-matching --max-count=1 --perl-regexp --regexp="[0-9]{4}-[0-9]{2}-[0-9]{2}" \ | tr --delete - \ ) if [[ -n $_due ]]; then due=$(date -d "$_due" +%s) now=$(date -d $(date +%Y-%m-%d) +%s) if [[ $now -ge $due ]]; then echo "$(formail -f -I 'X-TODO: OVERDUE' < ${mailfile} | cat )" > "${mailfile}" mflag -F "${mailfile}" > /dev/null 2>&1 fi fi done < <(find ~/Mail/To-do -type f -print) It adds a custom header X-TODO, based on which I mark respective messages with color: color index white red "~h '^X-TODO: OVERDUE$'" To propagate changes to the far side, along with adding the header, which is never syncing, I also add a flag, which does sync. Anyway, Gmail’s web interface does not support sorting by subject, so at least I can spot the starred messages of interest there. Best, -- Dmitry On Thu, Jul 7, 2022 at 4:40 PM dm1...@gmail.com <dm1...@gmail.com> wrote: > > Hi all, > > I have some messages with a subject line containing the "due:[here > goes some date]" text. I want mutt to color these messages differently > and dynamically (at every opening or refreshing the mailbox) according > to whether the date in the subject is in the past or the future > compared with the current date. > Is it possible to accomplish? > > It would be nice to enchance the "todo.txt" approach with the "to-do > mailbox" advantages :-) > > Best, > > -- > Dmitry