gistfile1.m

MCOSMTPSession *smtpSession = [[MCOSMTPSession alloc] init];
smtpSession.hostname = @"smtp.gmail.com";
smtpSession.port = 465;
smtpSession.username = @"matt@gmail.com";
smtpSession.password = @"password";
smtpSession.authType = MCOAuthTypeSASLPlain;
smtpSession.connectionType = MCOConnectionTypeTLS;

MCOMessageBuilder *builder = [[MCOMessageBuilder alloc] init];
MCOAddress *from = [MCOAddress addressWithDisplayName:@"Matt R"
                                              mailbox:@"matt@gmail.com"];
MCOAddress *to = [MCOAddress addressWithDisplayName:nil 
                                            mailbox:@"hoa@gmail.com"];
[[builder header] setFrom:from];
[[builder header] setTo:@[to]];
[[builder header] setSubject:@"My message"];
[builder setHTMLBody:@"This is a test message!"];
NSData * rfc822Data = [builder data];

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

smtpSession.authType = (MCOAuthTypeSASLPlain | MCOAuthTypeSASLLogin);
It's misleading, authType is not supposed to be a bit mask.
Could you remove it?

Yeah, my bad. I was confused about authType...