Command in custom header

[fugo]

Evolution 3.46.4 Arch Linux
I want to use a command in a custom header.
Is this possible?
I need the date command to schedule my mails.
like date --rfc-email -d '1 day 10:00'
My email provider can handle this with a schedule IMAP folder.

[mcrha]

Hi,
the custom headers plugin allows only static strings, not commands.

If you want this to schedule the send time by saving the message to a
certain folder on the server, instead of sending it, then you can use
an Outgoing Filter (in Edit->Message Filters, change the type at the
top), where you can “Pipe To Program” and that program can add the
header at (the top of) the message. You can even configure your IMAP
account to use ‘sendmail’ instead of SMTP and have the filter store the
message into the right folder. Unless it’s the SMTP server which
understands that date header; I’m not sure from your text how it is.

You can also create a composer plugin, which will do all of it for you.
An example of it is here:
https://wiki.gnome.org/Apps/Evolution/Extensions#Example_Module

Bye,
Milan

[fugo]

Thank you,
I will take a closer look on filters.