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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36
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5answers
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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 ...
31
votes
6answers
37k views

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. ...
11
votes
3answers
34k views

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 ...
9
votes
1answer
6k views

mutt SMTP TLS error sending mail

When I try to send a mail, I get the following error: gnutls_handshake: An unexpected TLS packet was received. This is my .muttrc (myname, myaddress and mymail are placeholders): # Automatically ...
9
votes
1answer
23k views

How to Allow Outgoing SMTP on iptables Debian Linux

If I choose to allow all traffic on the OUTPUT chain (iptables -P OUTPUT ACCEPT) mail sends fine. As soon as I lock down my server with these rules, outgoing mail stops working. All else works though, ...
7
votes
1answer
10k views

Postfix: disable authentication through port 25

When using Postfix and IMAP on a mailserver, at least 3 ports are usually opened 25 smtp : incoming emails from anybody (whole internet) 465 smtps : outgoing emails from authorized users (to the ...
6
votes
1answer
2k views

Changing SMTP authentication in mutt based on From e-mail address

I use mutt as my e-mail reader, and nbSMTP as my SMTP client. I check e-mail from a half dozen accounts and sort them into miscellaneous folders in my maildir. Some of the folders are account-specific,...
5
votes
2answers
4k views

How to configure Exim to forward all incoming mail to new server?

I am moving servers, both of them running Debian (oldstable and stable). Both are running Exim4. When I switch the DNS entries over to the new server, I'd like the old server to still forward incoming ...
5
votes
2answers
4k views

Check SMTP server capabilities on the command line

I know an SMTP server's URL. I want to know about that SMTP server's capabilities: TLS, password encryption, etc. Evolution Mail knows how to report these. How can I get them from the command line? ...
4
votes
2answers
7k views

Why I can't send mail to remote mailbox?

I have installed Postfix on my CentOS machine. I can nicely send mails to local accounts with mutt, but when I try to send one to a remote mail like myactualmail@gmail.com, I cannot understand why I ...
3
votes
2answers
2k views

Too many smtpd daemon forks?

I have many forks from smtpd in my process list on my webserver. What does this mean? Is my mailbox full? postfix 2662 0.0 0.9 106336 4856 ? S 17:37 0:00 smtpd -n smtp -t ...
3
votes
2answers
2k views

Protecting postfix from bruteforce attacks

a few days ago I've set up a VPS, including personal SMTP service using postfix + procmail under Debian / Wheezy. I am already seeing a LOT of hammering onto the SMTP and other ports. Here's an ...
3
votes
4answers
880 views

ssh public keys instead of SASL for authenticated SMTP sending?

I'm currently using postfix and SASL on my personal server for authenticated SMTP. The server is purely for my personal use and my personal domains, so I'd much rather have something simpler based on ...
3
votes
1answer
898 views

Reverse DNS does not match SMTP Banner for multidomain hosting

We are planing for mail hosting, we are going to host multiple customer mail domain on single public IP. Now how i am going to set PTR record per customer? because i have single IP and it has to be ...
3
votes
2answers
960 views

sendmail not sending to the cloud (local mail works)

I'm using a perl module (Mail::Sendmail) which uses sendmail to send stuff. It hasn't been working, but hasn't been giving me any errors. So now I suspect sendmail. I tried: telnet 127.0.0.1 25 mail ...
3
votes
1answer
4k views

How do I email root?

I am on Debian squeeze and I'd like to forward my root emails to my real email. I setup exim to use gmail so when I write mail myname@myemail.com it sends to my email. However, now I'd like to email ...
3
votes
1answer
130 views

What is the correct helo for a smtp server that does not receive mail and does not have a FQDN?

What is the legal and correct helo for my SMTP server. Out going email only. Behind a NAT with no inbound ports open. SMTP server does not have a FQDN. Send mail for 2 different domains We are a ...
3
votes
1answer
1k views

How to send non-local mail, with GMail(GApps) SMTP?

I have some (~3) Debian boxes, and I want to post system mail to my non-local mailbox. But I have a problem with configuring exim4. Also I don't like so much exim4's config. Too different, and also ...
3
votes
0answers
40 views

How to force use SMTP servers in Alpine?

Does anybody know how to force Alpine to use a particular SMTP server from the config list? It seems to choose the first server in the SMTP list in config, but I want to be able to choose the SMTP ...
3
votes
2answers
1k views

how to find out the full path of the command from the result of lsof -i

lsof is a great utility, just now started using it. lsof -i | grep smtp => this give the following result. httpd.pl 212548 global 3u IPv4 893092369 0t0 TCP server07.host...blah.....
2
votes
4answers
25k 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 ...
2
votes
2answers
577 views

Lightest weight SMTP server for Linux Single Board Computer (SBC)

The other discussions I found did not give a clear answer to my question. Problem description: I am running an embedded Linux server device, such as TuxRail or a DreamPlug which are ARM-based devices ...
2
votes
1answer
182 views

Question about MX records and mail delivery?

Let's say, we have multiple mail servers in DNS records. If someone is sending a mail, the outgoing mail server will check the MX and contact the first server with the lowest cost. If this server ...
2
votes
2answers
1k views

Recommendations for good MTA / groupware solutions?

I'm setting up a Debian server, and one of the things I need on it is an MTA. I don't want to use something like Exim or Postfix because I want something that ties in SMTP, POP3, and IMAP all in one (...
2
votes
1answer
254 views

Trying to send multiple text attachments via mail message

Running this script on: "Red Had Enterprise Linux Server release 5.11 (Tikanga)" Mail is: version 8.1 6/6/93 (appears quite old). Have tried various things and cannot seem to get this to work.. ...
2
votes
2answers
18k views

Using port 587 with sendmail

I have been using sendmail to send out mails using internally available mail server. But currently port 25 is blocked for security reasons. I would like to know if there is a way to specify port ...
2
votes
1answer
4k views

mails being marked as spam

I configured my own mail server using sendmail for our application . Mail server is used to send automated mails when a user registers at our site . I was able to implement this successfully, but ...
2
votes
2answers
603 views

Alpine using localhost address

I'm having a hard time figuring out what's going on with my setup, first there's no problem with the imap part as I can see my email, but when I try to send a message I get this error: [Mail not sent....
2
votes
1answer
448 views

How are email headers generated?

When you send an email a header is part of the message. For example, when you check your mail you can view the raw source and see the headers, which has information about the sender of email in it, ...
2
votes
2answers
1k views

Is there a way to completely disable outbound opportunistic TLS support in SendMail?

CentOS 5.x SendMail 8.14.4 An overzealous network security feature is causing TLS negotiations to fail when my Sendmail server tries to talk to external hosts. This is causing sendmail to constantly ...
2
votes
2answers
188 views

IPTABLES to allow ssh, ftp, pop, etc from one static IP address with HTTP/SSL open to public

This is my setting in /etc/sysconfig/iptables: #start of my iptables # Generated by iptables-save v1.2.11 on Wed May 27 00:31:22 2015 *mangle :PREROUTING ACCEPT [130933577:29488298585] :INPUT ...
2
votes
1answer
647 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 /usr/lib/...
2
votes
1answer
814 views

Relay access error when I try to send mail from outside to postfix

I run a debian 7 system and I run postfix as smtp server. I can send mail from postfix to outside (even though it gets to spam folders by google) but when I try to send a mail from, lets say my google ...
2
votes
2answers
335 views

Sending mail to lan ip failed

In a Ubuntu os, with sendmail installed (maybe as default installed package) but not configured, I tried to type both echo "Text message" | mail <dest_ip_address>\!dest_user and echo "Text ...
2
votes
1answer
276 views

Check SMTP over SSL

I need to get a look at how my SSL mailserver plays with others; for non-SSL this is easy to do with (e.g.) telnet. Is there a bonified SSL/TLS client that can be used the same way?
2
votes
1answer
539 views

Why doesn't Postfix reject a specific client's connection attempts?

My SMTP server is being probed. It looks like a brute force attach on SASL, where they're going through a password dictionary. Having seen thousands of these lines in the log files Sep 18 14:09:52 ...
2
votes
2answers
320 views

Considerations when hosting an outgoing email server

I want to host an email server on my VPS so I can send automated emails from my application. Reading about the different ways of hosting email servers (involving ISPs blocking ports, open relay ...
2
votes
1answer
644 views

OpenSMTPD Configuration Problem

I'm trying to configure a simple mail server on OpenBSD 5.2, running OpenSMTPD 5.3.1, however there is some problem with my configuration file, and I'm unsure how to fix it. I can send and receive ...
2
votes
2answers
347 views

outgoing SMTP 25 port blocked by ISP?

I just setup postfix but I just realized my ISP outgoing blocks port 25 (SMTP). How do I send email outside? I can see my mail queue is filling up. Any suggestion?
2
votes
1answer
334 views

Can Apache Web server Respond to SMTP/IMAP/POP3 requests?

Bear with me, please. I want to know what functions are provided by the Apache 2.4.9 Web server on Fedora 20. I understand that Apache responds to HTTP request only. I believe that SMTP and POP3 ...
2
votes
2answers
2k views

setting up mail system

So I'm still kind of new to linux, but what are the steps towards setting a linux box up in such a way that it can send mail using shell? echo "hello world" | mail johnny@moo.com I mean, I've done ...
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. other@remote.com....
2
votes
1answer
67 views

Local E-Mail sink

I do have multiple mail accounts (personal, university, work, …). Currently I'm connecting from every device (notebook, smart phone, tablet,…) to each of them via IMAP . Setting up multiple IMAP and ...
2
votes
0answers
153 views

SMTP works via Mail client but not via openssl

I'm trying to troubleshoot an SMTP issue. My credentials work fine via the OS X Mail client (and in other areas), so the credentials are definitely good. However, when I try to submit them via: ...
2
votes
1answer
198 views

How to configure SMTP with postfix with user and pass

I'm looking for a way to enable postfix (or any other mail delivery system) in which I can easily have aliases (user and domain aliases), and in which I can have an external user send mails through ...
2
votes
0answers
335 views

Confirm DavMail connection

I am using DavMail to connect to my employers Outlook servers. Before I attempt to configure the email client to work with DavMail, I want to confirm that DavMail has been configured properly and is ...
2
votes
0answers
722 views

Impossible to send mail to microsoft (hotmail, live …)

I cannot send mail to hotmail with my postfix server. I can send and receive mail from gmail and others, but not hotmail. I made an "Authentication Report" on auth-results@verifier.port25.com: ======...
2
votes
1answer
2k views

SMTP connectivity issue in Zenoss (“Connection unexpectedly closed”)

I am using Zenoss for monitoring purpose. I have been using its mail service for a long time. Suddenly my mail service in zenoss stopped and started showing <class 'smtplib.SMTPServerDisconnected'&...
2
votes
1answer
680 views

Trouble with postfix install (timing out from client) [closed]

I have just outfitted a basic server (Ubuntu 12.04 LTS /Precise Pangolin) and have installed Postfix and Dovecot, based on the Ubuntu manuals. https://help.ubuntu.com/community/Dovecot https://help....
2
votes
0answers
3k views

SMTP Auth - SASL on Dovecot, Postfix and CentOS 6.2 (and Open-Xchange)

I am trying to get open SASL to work on CentOS 6.2. I followed this tutorial: http://wiki.centos.org/HowTos/postfix_sasl I suspect it works perfectly for CentOS 5.x so all I really need is an update ...