Disclaimer: this is very likely not safe, use it at your own risk, I don’t account for any harm.

So you can’t remove messages with notmuch:

While notmuch does not support, nor ever will, the deleting of messages...

That’s a fact. But what if it could help you with that? A lot actually.

I reached my quota. And there was no way to remove messages in bulk with standard web interface (I wanted to get rid of ~30k messages). The filter I wanted to use was quite simple:

Everything older than one year from these folders.

This is where notmuch excells!

So I tagged the mail for deletion:

$ notmuch tag +deleted date:..1.5year folder:chatty-mailing-list

So we know now what we want to delete. Let’s proceed to mbsync part. And this is where it gets messy and dangerous. I definitely advise to turn off any mail synchronization. So there are no race conditions in-place.

First set Expunge to Both since you want to remove your remote mail.

Time for some maildir flags magic: if you flag your mail with T, it means it’s suppose to be trashed. Our mail server actually removes it right away. So let’s trash:

$ for x in $(notmuch search --output=files tag:deleted) ; do mv $x ${x}T ; done

It seems simple, but it’s definitely not safe b/c it is expected that message file ends with 2,, so please make sure the filenames look like this:

/home/me/.mail/chatty-mailing-list/cur/1437473681.4267_139480.host,U=13261:2,

so you can trash them by turning them into

/home/me/.mail/chatty-mailing-list/cur/1437473681.4267_139480.host,U=13261:2,T

Run mbsync, it will propagate the deletion and… That’s it.

This has worked for me, I hope it will work for you. Just make sure what you’re doing before running any potentially destructive commands.

Is there a better way? I think so. Please suggest in comments.