// build session with credentials and authentication
        NSString *smtpHostname = @"mrint.1and1.com";
        NSUInteger smtpPort = 587;
        NSString *smtpUsername = @"<intranetuser>";
        NSString *smtpPassword = @"<password>";
        NSString *fromEmail = @"<email?";
        NSString *fromDisplayname = @"Peter Breitling";

        MCOSMTPSession *smtpSession = [[MCOSMTPSession alloc] init];
        smtpSession.checkCertificateEnabled = NO;
        smtpSession.hostname = smtpHostname;
        smtpSession.port = (unsigned int) smtpPort;
        smtpSession.username = smtpUsername;
        smtpSession.password = smtpPassword;
        smtpSession.connectionType = MCOConnectionTypeStartTLS;

        //smtpSession.authType = MCOAuthTypeSASLPlain;
        //smtpSession.authType = MCOAuthTypeSASLNone;

        // build from

        MCOMessageBuilder * builder = [[MCOMessageBuilder alloc] init];
        [[builder header] setFrom:[MCOAddress addressWithDisplayName:fromDisplayname mailbox:fromEmail]];
        //[[builder header] setFrom:[MCOAddress addressWithRFC822String:fromEmail]];

        // build to, cc and bcc adresses

        NSMutableArray *to = [[NSMutableArray alloc] init];
        for (NSString *email in [mail sortedToMailContacts])
        {
            [to addObject:[MCOAddress addressWithMailbox:email]];
        }
        [[builder header] setTo:to];
        NSMutableArray *cc = [[NSMutableArray alloc] init];
        for (NSString *email in [mail sortedCcMailContacts])
        {
            [cc addObject:[MCOAddress addressWithMailbox:email]];
        }
        [[builder header] setCc:cc];
        NSMutableArray *bcc = [[NSMutableArray alloc] init];
        for (NSString *email in [mail sortedBccMailContacts])
        {
            [bcc addObject:[MCOAddress addressWithMailbox:email]];
        }
        [[builder header] setBcc:bcc];

        // subject, text- & html-body

        [[builder header] setSubject:mail.subject];
        builder.textBody = mail.textBody.content;
        builder.htmlBody = htmlBody;

        // attachments

        //        MCOAttachment *attachment = [MCOAttachment attachmentWithContentsOfFile:path];
        //        [builder addAttachment:attachment];
        NSData * rfc822Data = [builder data];
        smtpSession.connectionLogger = ^(void * connectionID, MCOConnectionLogType type, NSData * data){
            NSLog(@"smtp session[%li] %@", (long)type, [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
        };

        MCOSMTPSendOperation *sendOperation = [smtpSession sendOperationWithData:rfc822Data];
        [sendOperation start:^(NSError *error) {
            if(error) {
                NSLog(@"Error sending email:%@", error);
            } else {
                NSLog(@"Successfully sent email!");
            }
        }];