Once upon a time, Muhammad Yousuf Khan <sir...@gmail.com> said: > now the confusion part is my concept. does port 25 and 465 work together > like FTP. port 21 and 20. like 1 port is for negotiate and another port is > for data?
Port 25 is tradtiotional SMTP, aimed at server<->server communications now (and blocked by some consumer ISPs to reduce spam). It starts in the clear but can support STARTTLS to switch to encrypted communication. Port 587 is the "submission" port for SMTP. It works the same as port 25 (including clear communications and STARTTLS support), but is intended for client<->server communication for initial message submission. It should require SMTP AUTH (so only authenticated mail can be submitted). Port 465 was an early (non-standard) SSL-wrapped SMTP port. All communication is encrypted (similar to port 443 for HTTP). This was never an IANA-assigned use, and not that many things support it. Its use is deprecated, but MS Outlook (at least some versions) only support SSL-wrapped SMTP on port 465 (they don't handle the standard way of connecting to 587 and then issuing STARTTLS). -- Chris Adams <c...@cmadams.net>
