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smtp

Posted on 2011-09-08
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Last Modified: 2012-05-12
This may be a dumb question.

Let's say a device is configured with an SMTP server so that it can relay emails.

Is the device sending emails to the specified SMTP server and then the SMTP server sends it to the intended recipients mali server?
That would mean device sends to smtp server on port 25, smtp server sends to the recipients mail server on port 25. Recipients mail server sends it to the mailboxes on port 25?

 
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Question by:trojan81
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by:madhatter5501
ID: 36506500
you are correct, if you are interested in how many servers a email travels through before you receive it, check out the message headers some time.

http://ask-leo.com/how_do_i_view_full_mail_headers_in_outlook.html
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by:Alan Hardisty
Alan Hardisty earned 133 total points
ID: 36506533
Let's break this down:

That would mean device sends to smtp server on port 25 - not necessarily - any port can be used it all depends on how the server is configured and what version of Exchange.

smtp server sends to the recipients mail server on port 25 - Yes - port 25 is the standard port for all mail server to receive mail from other mail servers.

Recipients mail server sends it to the mailboxes on port 25? - Nope - it doesn't use SMTP to transfer the mail from the mail server to the mailbox.
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by:madhatter5501
madhatter5501 earned 133 total points
ID: 36506563
my bad, depending on the technology the server will send to the recipient on port by default

POP3 - port 110
IMAP - port 143
SMTP - port 25
HTTP - port 80
Secure SMTP (SSMTP) - port 465
Secure IMAP (IMAP4-SSL) - port 585
IMAP4 over SSL (IMAPS) - port 993
Secure POP3 (SSL-POP) - port 995
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tsaico earned 134 total points
ID: 36506636
For the most part, but not in all situations for the end email clients tend to be on a different protocol for grabbing mail.  Port 25 is for between servers, and between server and end user is usually a protocol like IMAP, MAPI, or POP3.  In some cases RPC-HTTP will "reuse" often open ports 80 and 443 for this function.

So depending on situation, my workstation will use and IMAP port 585 for it's inbound mail, meaning the server is sending over IMAP to my computer.  The server received it from the outside world on 25 though. So you are right, with the exception of the end statement of "Recipients mail server sends it to the mailboxes on port 25", where my interpretation of mail box is my connection on my device.
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