SMTP, Application layer ?

SiLentThReaD

SMTP runs on the upper layers, above the applications layer.

Can we say that SMTP is a form of software gataway ?

Webmaster

Not above the application layer, but on it.

Can we say that SMTP is a form of software gataway ?

In some remote ways, you could say that... I wouldn't though Especially not in terms of CompTIA...
SMTP is a protocol. A gateway can be software that translates between protocols, but STMP connects to SMTP... i.o.w. there are no gateways that translate from POP3 to SMTP.

But oif you have a dedicated server with 'SMTP relay' software on it, you could consider it as being an SMTP gateway (for e.g. forwarding all SMTP traffic in an internal network that is meant to go to the Internet.)