I have looked at the MS Docs for this:
Which states (emphasis mine)
SMTPConnectionTimeout: Specifies an integer value indicating the number of seconds to wait for a valid socket connection with the SMTP service before timing out. The default is 30 seconds, but this value is ignored if SendUsing is set to 2.
Of course we are configured exactly that way
So does anyone know what the default value is in that case specifically? Or does this mean the "default is 30 seconds and it cannot be overridden if SendUsing = 2"?
Pointers to a authoritative source are very much appreciated.