tcp port 25 is the type of email server that is typically used for outgoing mail.
tcp port 25 is the type of email server that is typically used for outgoing mail.
which type of email server is typically used for outgoing mail?
tcp port 25
a server that is accessible on the wider internet and does not enforce these kinds of access restrictions is known as an open relay. this is now generally considered a bad practice worthy of blacklisting.









































section::::outgoing mail smtp server.:ports.









































communication between mail servers generally uses the standard tcp port 25 designated for smtp.









































mail "clients" however generally don't use this, instead using specific "submission" ports. mail services generally accept email submission from clients on one of:









































bullet::::- 587 (submission), as formalized in (previously )









































bullet::::- 465 this port was deprecated after , until the issue of rfc 8314.
simple mail transfer protocol
to combat the problems posed by botnets, open relays, and proxy servers, many email server administrators pre-emptively block dynamic ip ranges and impose stringent requirements on other servers wishing to deliver mail. forward-confirmed reverse dns must be correctly set for the outgoing mail server and large swaths of ip addresses are blocked, sometimes pre-emptively, to prevent spam. these measures can pose problems for those wanting to run a small email server off an inexpensive domestic connection. blacklisting of ip ranges due to spam emanating from them also causes problems for legitimate email servers in the same ip range.
email spam