Scripting a Zoho catch-all filter

October 18, 2023

I use Zoho as my email provider, and I recently learned that you can setup a catch-all forwarding address. This is pretty great, because that means I can receive any email sent to my domain! Go ahead, try it.

I want to sort the emails I receive into their own folder, though, depending on the delivery address (for example, lol@miccah.io will go to /catch-all/lol). It turns out, Zoho supports custom mail filters using a scripting DSL called deluge, so I wrote one!

At a high level, the filter parses the To address of the email, creates the folder if it does not exist, then moves the email into that folder. In order to work properly, I needed to create a “connection” with the properly scoped permissions: ZohoMail.messages.READ, ZohoMail.messages.UPDATE, and ZohoMail.folders.ALL. This will be clear if you’re going through the process yourself, otherwise don’t worry about it.

Here’s the script in all it’s glory. I had fun hacking on this and was pleasantly surprised that it was a feature available to me!

info "Use the 'To' address to create a subfolder in catch-all and move the message there";
conn = "catchallfilter";
messageID = mail_messageId;
messageDetails = zoho.mail.getMessage(messageID, conn);

// Parse address for the folder name.
// toAddress is of the form "&lt;ADDR@domain.com&gt;"
toAddress = messageDetails.get("TO");
newName = toAddress.subString(4, toAddress.indexOf("@"));
info "routing to " + newName;

// Search top-level folders for "catch-all", then search its children for
// newName. If it's not found, create it.
for each folder in zoho.mail.getFolders(conn) {
	folderName = folder.get("NAME");
	if (folderName != "catch-all") {
		continue;
	}
	catchallSubFolders = folder.get("CHILDREN");
	subFolderExists = false;
	for each subFolder in catchallSubFolders {
		if (subFolder.get("NAME") != newName) {
			continue;
		}
		subFolderExists = true;
		info "subfolder exists";
		break;
	}
	if (!subFolderExists) {
		info "creating subfolder";
		zoho.mail.createFolder(newName, folder.get("ID"), conn);
	}
	break;
}
info "moving to subfolder";
zoho.mail.moveToFolder(messageID, "/catch-all/" + newName, conn);