Complex sentence: SMTP was seen as particularly important, because client s of this protocol foreign server address, which cannot know whether they have a separate port for TLS The port 465 is now registered "for" Source Specific Multicast audio and video.
Split into simpler sentences: SMTP was seen as particularly important, because client s of this protocol foreign server. Address, which cannot know whether they have a separate port for TLS The port 465 is now registered "for" Source Specific Multicast audio and video.