Strange behaviour with outgoing mails

Dear community,

I was wondering if this is just me, as outgoing mails take time to be processed by the XG firewall.
In my case, an email hangs in the queue for about one to two minutes until it is sent from the XG to the WAN. The email does not even have an attachment and is about 8 KB in size.
Furthermore, according to the log it was sent three times although I only replied and sent it once using the Gmail client.

Is this a bug or did I some misconfiguration here?

Using XG SFOS 18.0.0 EAP2.