--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/nabble/model/MailSubsystem.java	Thu Mar 21 19:15:52 2019 -0600
@@ -0,0 +1,133 @@
+package nabble.model;
+
+import fschmidt.util.mail.Content;
+import fschmidt.util.mail.Mail;
+import fschmidt.util.mail.MailAddress;
+import fschmidt.util.mail.MailHome;
+import fschmidt.util.mail.MailParseException;
+import fschmidt.util.mail.MixedMultipartContent;
+import fschmidt.util.mail.PlainTextContent;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+
+
+final class MailSubsystem {
+	private static final Logger logger = LoggerFactory.getLogger(MailSubsystem.class);
+
+	private MailSubsystem() {}  // never
+
+	/**
+	 * Send an error message.
+	 *
+	 * @param mail      a mail caused a message, may be null
+	 * @param mailTo    sent error message to
+	 * @param subject   message subject
+	 * @param errorText error text
+	 */
+	static void sendErrorMail(Mail mail, MailAddress mailTo, String subject, String errorText) {
+		Mail errMail = MailHome.newMail();
+		errMail.setFrom(new MailAddress(ModelHome.noReply));
+		errMail.setTo(mailTo);
+		errMail.setSubject(subject);
+		errMail.setSentDate(new Date());
+		Content content = (mail != null) ?
+				new MixedMultipartContent(new Content[]{
+						new PlainTextContent(errorText),
+						mail,
+				}) :
+				new MixedMultipartContent(new Content[]{
+						new PlainTextContent(errorText)
+				});
+		errMail.setContent(content);
+		ModelHome.send(errMail);
+	}
+
+/*
+	static String stripBrackets(String s) {
+		if (s == null) return null;
+		int start = s.lastIndexOf('<');
+		int end = s.lastIndexOf('>');
+		if (start >= 0 && end > start)
+			s = s.substring(start + 1, end);
+		return s.trim();
+	}
+*/
+	static String stripBrackets(String s) {
+		int start = s.lastIndexOf('<');
+		int end = s.indexOf('>');
+		if( start == -1 && end == -1 )
+			return s;
+		if( start == -1 || end < start )
+			throw new MailParseException("no brackets found in '"+s+"'");
+		return s.substring(start + 1, end);
+	}
+
+	static List<String> stripMultiBrackets(final String s) {
+		List<String> list = new ArrayList<String>();
+		for( int i=0; i<s.length(); ) {
+			int start = s.indexOf('<',i);
+			int end = s.indexOf('>',i);
+			if( start == -1 && end == -1 )
+				break;
+			if( start == -1 || end < start )
+				throw new MailParseException("malformed brackets found in '"+s+"'");
+			list.add( s.substring(start + 1, end) );
+			i = end + 1;
+		}
+		return list;
+	}
+
+
+
+
+	/**
+	 * Prepare message headers for sending
+	 *
+	 * @param mail	   to prepare
+	 * @param node	   node to be sent
+	 */
+	static void setHeaders(Mail mail, NodeImpl node) {
+		mail.setSentDate(new Date());
+		mail.setMessageID("<" + node.getOrGenerateMessageID() + ">");
+		NodeImpl parent = node.getParentImpl();
+		if (parent != null && parent.getKind() != Node.Kind.APP) {
+			mail.setHeader("In-Reply-To", "<" + parent.getOrGenerateMessageID() + ">");
+			mail.setHeader("References", getReferences(parent, 0).trim());
+		}
+	}
+
+	private static final int MAX_REFERENCES = 10;
+
+	private static String getReferences(NodeImpl node, int count) {
+		return (node == null || node.getKind() == Node.Kind.APP || count==MAX_REFERENCES) ?
+				"" :
+				getReferences(node.getParentImpl(), count+1) + " <" + node.getOrGenerateMessageID() + ">";
+	}
+
+
+	static String getReturnPath(Mail mail) {
+		String[] a = mail.getHeader("Return-path");
+		return a==null ? null : MailSubsystem.stripBrackets(a[0]);
+	}
+
+	static void bounce(Mail mail,String msg) {
+		Mail bounce = MailHome.newMail();
+		bounce.setFrom( new MailAddress(ModelHome.noReply,"Nabble") );
+		bounce.setTo( new MailAddress(getReturnPath(mail)) );
+		bounce.setSubject( "Delivery Status Notification (Failure)" );
+		bounce.setHeader( "X-Failed-Recipients", mail.getHeader("Envelope-To") );
+		StringBuilder content = new StringBuilder();
+		content
+			.append( msg )
+			.append( "\n----- Original message -----\n\n" )
+			.append( mail.getRawInput() )
+		;
+		bounce.setContent(new PlainTextContent(content.toString()));
+		ModelHome.send(bounce);
+	}
+}
+