mrep: Set From header according to To/Cc header

[nmeum]

I use different mail addresses for different purposes. When replying to
any email, mrep(1) currently uses the mail address configured as
Local-Mailbox for the From header. While generally desirable, I do not
want to reply to mails I received through my work address with my
private email address.

This commit introduces a change which uses the email address, the email
was sent to, (as specified by To/Cc) for the From header, as long as this
address was configured as an Alternate-Mailboxes. I just quickly hacked
this together as a proof of concept without much further considerations.
Seems to work though but not sure if it is generally desirable to enable
this behaviour by default, let me know what you think.

[leahneukirchen]

This is a good idea, but there are some cases that require more thought: if you are in Cc with address only, your from doesn't contain the real name e.g.

Probably an improvement over the status quo, however.

[nmeum]

Good point, RFC 5322 addresses complicate this setup quite a bit. For example, my assumption was that Alternate-Mailboxes just contains the mail address but that's not necessarily the case, right? If so, it would probably make sense to modify grepmine in a way that it operates only on the mail address part and later map that address to the display name using a different function? Is there already any tool for extracting the display-name/mail-address part of an RFC 5322 address?

[leahneukirchen]

I think alternate-mailboxes should just contain the addresses.

maddr -a can print the address only, i guess adding maddr -d would be useful.

[Duncaen]

magrep with -a would be a good instead of grep, but it only matches all headers or one header at a time.

$ magrep -ha "to:mail@duncano.de|administrator@duncano.de" 100
to: administrator@duncano.de
$ mhdr -h to 100
Duncan Overbruck <administrator@duncano.de>

Edit: nvm, this doesn't really solve the problem, but might be better than a plain grep if someone messes with comments in addresses etc.

[nmeum]

I think alternate-mailboxes should just contain the addresses.

Good to know, but the Local-Mailbox should definitely contain a valid RFC 5322 address, or at least mine does. In general, it might makes sense to use this as is and improve it later on when tooling around RFC 5322 has improved? idk.

[leahneukirchen]

Perhaps we can use a different header in the configuration for this feature. Then map that by address to the given displayname.

[nmeum]

Just to make sure I understood you correctly: You are proposing adding an additional header to mblaze-profile(5) which contains a display name which is then combined with the address extracted from the To/Cc header and used as the From header in the reply?

[leahneukirchen]

Exactly.

[leahneukirchen]

I added maddr -d.

[leahneukirchen]

not sure we need that actually, but it's an obvious feature.

[nmeum]

I added maddr -d.

Pushed a change which utilities maddr -d to extract the description part form the local-mailbox and combines that with the address extracted from the To/Cc/Bcc header. I haven't handled the case where the local-mailbox configuration header doesn't contain a description. However, this should address your original comment. I personally find that preferable to adding a new configuration header, let me know what you think.

not sure we need that actually, but it's an obvious feature.

I personally find it very handy, but if you don't want it that's fine as well.

[nmeum]

The more compilated version which also handles a missing description in local-mailbox would be:

addr=$(maddr -a -h to:cc:bcc: "$1" | grepmine | head -n 1)
if [ -n "$addr" ]; then
	desc=$(maddr -d -h "local-mailbox" "$MBLAZE/profile")
	if [ -n "$desc" ]; then
		from=$(printf "%s <%s>" "$desc" "$addr")
	else
		from=$addr
	fi
else
	from=$(mhdr -h local-mailbox "$MBLAZE/profile")
fi

[leahneukirchen]

Well, I have some private addresses that are listed as Alternative-Mailboxes to get the > sign, but that I don't use for replying. Also, people could use From: addresses that are not in Alternative-Mailboxes (e.g. a shared helpdesk email).

[nmeum]

Well, I have some private addresses that are listed as Alternative-Mailboxes to get the sign, but that I don't use for replying.

It would certainly be possible to add a new auto-reply-addresses profile header setting (or something along the lines).

Also, people could use From: addresses that are not in Alternative-Mailboxes (e.g. a shared helpdesk email).

Why would that be a problem? Unless I am missing something here the code should fallback to local-mailbox then.

If you generally disagree with the feature I will just apply my patch locally. If you like the idea in general but don't like the implementation I can try to adjust it. Either way is fine with me.

[leahneukirchen]

I'm thinking of a slightly more general feature, something like

replyfrom() {
        addrs="$(maddr -a -h reply-from "$MBLAZE/profile")"
        grep -Fv -e "addrs"
}
addr=$(maddr -a -h to:cc:bcc: "$1" | replyfrom | head -n 1)
if [ -n "$addr" ]; then
	from=$(maddr -h reply-from "$MBLAZE/profile" | grep -xi -e "<$addr>" | head - n1)
fi
if [ -z "$from" ]; then
	from=$(mhdr -h local-mailbox "$MBLAZE/profile")
fi

[leahneukirchen]

We could default addrs to alternative-mailboxes if reply-from is empty (having full names there should also be ok).

[nmeum]

I'm thinking of a slightly more general feature, […]

Sure, that would work for me 👍

[nmeum]

Implemented (i.e. copied) your implementation. Also added some documentation to mblaze-profile(5). The downside of this implementation is that you end of with a lot of duplicate address in mblaze-profile(5) at least for my simple use-case.

[leahneukirchen]

We could default to Alternative-Mailboxes when Reply-From is unset.

Sorry, I lost track of this PR in my todo list.

[nmeum]

We could default to Alternative-Mailboxes when Reply-From is unset.

Sure but imho that would complicate the code a bit (more case distinctions) as the fallback is needed both here:

mblaze/mcom

Lines 19 to 20 in 4e4dcdf

	addrs="$(maddr -a -h reply-from: "$MBLAZE/profile")"
	grep -F -e "$addrs"

and here:

mblaze/mcom

Line 367 in 4e4dcdf

from=$(maddr -h reply-from "$MBLAZE/profile" | grep -Fi "<$addr>" | head -n1)

Sorry, I lost track of this PR in my todo list.

So did I.

[nmeum]

Added some experimental fallback code.

[xelxebar]

Have my eye on this feature. The list of emails I have to reply as is very long and constantly growing. Would it make sense to allow wildcards or regex specifications in reply-from and/or alternative-mailboxes specifications?

Unfortunately * and / can technically appear in the local and domain parts, so we can't use an obvious wildcard syntax like *@example.com nor a regex syntax like /.*@example.com/. Unwinding the address specification in rfc5322 is a bit of a windy path, but it looks like we could get away with using \ of the specials (section 3.2.3). AFAICT the backslash can't appear anywhere in an address specification so a regex like \.*@example.com\ should be easily distinguishable and unambiguous.

Thoughts?

[leahneukirchen]

Do we really need something more complicated than @example.com?

[leahneukirchen]

I mangled this into 282de65, please test.

[xelxebar]

Do we really need something more complicated than @example.com?

Beautiful.

I mangled this into 282de65, please test.

Thank you. Will do.