SMTP is a protocol built upon TCP/IP, used for outgoing email transmissions, and email relaying. It uses ports 25 (clear) and 465 (SSL) by default.

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25
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6answers
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Lightweight outgoing SMTP server

What do you use as a lightweight SMTP for outgoing e-mails only? I am running an app that sends e-mails via SMTP when events occur once in a while, and I don't need a fully featured e-mail server. ...
9
votes
3answers
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How to “close” open ports?

A few days ago I started to care a lot about my data security, I end up nmaping myself with: nmap 127.0.0.1 Surprise, surprise, I have lots of active services listen to localhost: $ nmap 127.0.0.1 ...
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votes
1answer
1k views

setting up a relay port for postfix smtp on CentOS 7

A CentOS 7 server has postfix, dovecot, and mailx installed. I am able to make an IMAP connection to the server from my remote Thunderbird client running on my local devbox. But I am not able to ...
29
votes
5answers
77k views

Can I set up system mail to use an external SMTP server?

Is it possible to set up system mail on a linux box to be sent via a different smtp server - maybe even with authentication? If so, how do I do this? If that's unclear, let give an example. If I'm at ...
2
votes
1answer
234 views

assigning two ports to one service in firewalld

Is there a way to assign two ports to the same service in firewalld? For example, I would like for the SMTP service to listen on both port 25 and port 465. My first instinct is to change ...
2
votes
2answers
1k views

How to send mail from a remote SMTP host?

I have Postfix suite installed locally on Ubuntu 10.10. I can send/receive mail to my local address, e.g. user@local.com. I'm given credentials to a remote mail server mailbox, e.g. ...
1
vote
4answers
15k views

Helo command rejected: need fully-qualified hostname Error

My mail server is in some blacklist cause of spams. I reconfugured postfix. Aften then My customers get this error they can't send emails. 404 4.5.2 <PLLAMNAZIFE>: Helo command rejected: need ...
1
vote
0answers
140 views

How to disable SMTP auth plain for Citadel 8.20 on Slackware 14.0?

How do I turn off SMTP AUTH PLAIN for Citadel 8.20 on Slackware 14.0? If I set up postfix to handle SMTP would this allow me to not have SMTP auth plain enabled
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3answers
999 views

unable to view postfix email from centos 7 command line, why not?

I have postfix installed on a development box and I used the parameters from this other posting to configure postfix to work on localhost only. But the other posting does not explain how to send ...