There is this possibility in iGap to get to know the status of messages and whether is has been seen or not yet. Any type of your messages will be placed in a frame after sending. On the bottom of the frame there are a single/double check mark icon or a clock icon next to the time the message sent. Any of these check marks in their specific color means differently.
When a message is being sent, server receives it first and tries to get to connect with the recipient. Now you can see a single black check mark icon.
When server connects with the recipient, your message will get to her/him and there is a double check mark icon in black.
The double black check mark can turn to green immediately or after a while. It means your message was read by the recipient undoubtedly. If you send a voice message and the recipient saw and read it. not only the check marks get to green but also the time-indicator line of the message turns to green. Despite, the recipient just sees the voice message but does not listen to, the time-indicator line will be gray until it is heard.
On the bottom the message frame if you see the clock icon instead of the check marks, your message is being received by server; if it does not turn to the single black check mark, it is still waiting for the network connection. So, better to check your internet connection first.