In the Alert center (Settings > List settings > Alert center) you can configure an alert that is sent to you via email when there is a problem delivering a SMTP+ message. The message that is sent to you should contain details on why the message could not be sent.
However, please note that if the issue that you are experiencing is #4 above (the port is not open on the server), the message will have never left the server and therefore MailUp will never know about it. In that case, no alert can be sent as MailUp simply does not know of the message.
|Issue||What to do|
|Unable to send pictographs / symbols in subject line|
If your sending client does not support special characters in subject line, you can manually set the correct encoding. This is the format:
=?utf-8?Q?This is the subject text?=
Then to insert a symbol, enter his code (list of codes) and remember that each font can represent only a subset of all possible symbols. For example to insert a ♥ the subject needs to be:
=?utf-8?Q?I love you =E2=99=A5?=