Transfer protocol module that sends files as E-mail attachments

Install via "jsexec emailfiles -install". See comments for details.
This is the result of the script begun in this tutorial video:
https://youtu.be/1cSnF3Vq9XA

exec/emailfiles.js

+// File transfer protocol driver for the Synchronet Terminal Server
+// Sends file(s) via E-Mail attachment(s)
+
+// Make sure SCFG->Networks->Internet E-mail->Allow Sending of E-mail and
+// Allow File Attachments are set to "Yes".
+
+// Install using 'jsexec emailfiles.js -install'
+
+// Or manually in SCFG->File Options->File Transfer Protocols:
+
+// Mnemonic (Command Key)        E
+// Protocol Name                 E-mail Attachment
+// Download Command Line         ?emailfiles %f
+// Batch Download Command Line   ?emailfiles %s
+// Native Executable/Script      Yes
+// Supports DSZLOG               Yes
+// Socket I/O                    No
+
+// Your Synchronet Mail Server (SendMail thread) must be operational for this
+// module to work as expected.
+
+require("sbbsdefs.js", "K_EDIT");
+require('smbdefs.js', 'NET_INTERNET');
+require("text.js", "InvalidNetMailAddr");
+
+"use strict";
+
+if(argc < 1) {
+	alert("No filenames given");
+	exit(1);
+}
+
+var options = load({}, "modopts.js", "emailfiles");
+if(!options)
+	options = {};
+if(!options.maxsize)
+	options.maxsize = 10 * 1024 * 1024;
+
+if(argv[0] === '-install') {
+	var cnflib = load({}, "cnflib.js");
+	var file_cnf = cnflib.read("file.cnf");
+	if(!file_cnf) {
+		alert("Failed to read file.cnf");
+		exit(-1);
+	}
+	file_cnf.prot.push({
+		  key: 'E'
+		, name: 'E-mail Attachment'
+		, dlcmd: '?emailfiles %f'
+		, batdlcmd: '?emailfiles %s'
+		, ars: 'REST NOT M'
+		, settings: PROT_NATIVE | PROT_DSZLOG
+		});
+
+	if(!cnflib.write("file.cnf", undefined, file_cnf)) {
+		alert("Failed to write file.cnf");
+		exit(-1);
+	}
+	exit(0);
+}
+
+function sendfiles()
+{
+	var logfile = new File(system.node_dir + "PROTOCOL.LOG");
+	if(!logfile.open("w")) {
+		alert("Error " + logfile.error + " opening " + f.name);
+		return 1;
+	}
+
+	var msgbase = new MsgBase('mail');
+	if(!msgbase.open()) {
+		alert("Error " + msgbase.error + " opening mail base");
+		return 1;
+	}
+
+	var files_sent = 0;
+	for(var i = 0; i < argc; i++) {
+		var fpath = argv[i];
+		var fname = file_getname(fpath);
+		if(!file_exists(fpath)) {
+			alert(format("File (%s) does not exist", fname));
+			continue;
+		}
+		var size = file_size(fpath);
+		if(!user.is_sysop && size > options.maxsize) {
+			alert(format("File (%s) size (%u) larger than maximum: %u bytes"
+				,fname
+				,size
+				,options.maxsize));
+			continue;
+		}
+		var hdr = { subject: fname
+			,from: user.alias
+			,from_ext: user.number
+			,to: user.name
+			,to_net_type: NET_INTERNET
+			,to_net_addr: address
+			,auxattr: MSG_FILEATTACH | MSG_KILLFILE
+		};
+		if(!msgbase.save_msg(hdr, options.msg || "Your requested file is attached.")) {
+			alert("Error " + msgbase.error + " saving msg");
+			continue;
+		}
+		var dir = system.data_dir + format("file/%04u.out/", user.number);
+		if(!mkpath(dir)) {
+			alert("Error " + errno_str + " making directory: " + dir);
+			continue;
+		}
+		if(!file_copy(fpath, dir + fname)) {
+			alert("Error copying file: " + fname);
+			continue;
+		}
+		console.print(format(options.success || "Successfully sent: %s", fname));
+		console.crlf();
+		logfile.writeln(format("S %u infinite infinite 0 cps 0 errors 0 infinite %s -1"
+			,size, fpath));
+		files_sent++;
+	}
+	logfile.close();
+	msgbase.close();
+	return files_sent > 0 ? 0 : 1;
+}
+
+var result = 1;	// error
+if(!user.is_sysop && !(msg_area.inet_netmail_settings & NMAIL_ALLOW))
+	alert(bbs.text(NoNetMailAllowed));
+else if(!user.is_sysop && !(msg_area.inet_netmail_settings & NMAIL_FILE))
+	alert(bbs.text(EmailFilesNotAllowed));
+else {
+	console.print(options.prompt || "\x01h\x01yE-mail address: ");
+	if(!bbs.mods.emailfiles_address)
+		bbs.mods.emailfiles_address = user.netmail;
+	var address = console.getstr(bbs.mods.emailfiles_address, 60, K_EDIT | K_AUTODEL | K_LINE);
+	if(console.aborted || netaddr_type(address) != NET_INTERNET || address.indexOf('@' + system.inet_addr) >= 0)
+		alert(options.badaddr || "Unsupported e-mail address");
+	else {
+		bbs.mods.emailfiles_address = address;
+		result = sendfiles();
+	}
+}
+// The BBS flushes I/O buffers when returning from file transfers:
+while(bbs.online && console.output_buffer_level && !js.terminated) {
+	sleep(100);
+}
+exit(result);