I've been trying to install a Postfix server for handling mail for my domain. I found some nice tutorial and I was able to create email address and server responds correctly with telnet (imap and pop3 included, I also charge the config in Gmail and works correctly).
To handle POP3 and IMAP I have installed Courier
The problem comes when I try to send e-mails to myself (with external email address), I receive the following error code:
Action: failed
Status: 5.4.6
Diagnostic-Code: X-Postfix; mail for (servername) loops back to
myself
I reviewed my postfix mail.conf config, as in many webs they said that it could be because mydestination was not corectly configured. I have included the domain configuration and I still get the same error. (/etc/postfix/main.cf)
mydestination = mail.mydomain.com, domain.com, localhost
This is in a VPS, so the hostname is different to the domain name, I'm not sure if this can have any influence on the handling mail error.
Could someone help me to find where can the error be?
Thanks for your attention and your answers
You're probably sending mail to a recipient, with an email address in a zone which has an MX record, with its value a hostname, which resolves to the ip address of your mailserver, while this your server hasn't been told in its main.cf config file (behind mydestination), that it is referring to itself.
Therefore, your server is wondering why an attempt to send mail to - as it believes - another server results in finding that the ip address of that another server is its own ip address.
Update mydestination accordingly.
It helps to use the same hostname for MX record, for all zones your mailserver handles incoming mail for, as that keeps your mydestination manageable.
Related
Honestly, I think I have a fundamental gap in understanding how SMTP works. I can't seem to find a good explanation of what is happening behind the scenes and I think this is preventing me from being able to do what I am attempting to do.
To explain, I'm trying to setup an application which sends notifications to users by connecting to an SMTP server. Fair enough. I figure, since I'm using my own domain, I have SPF/DKIM/DMARC configured, I can add an MX record for the host I set the application up on (my SPF record has the mx keyword to authorize any hosts in my MX records to send/receive mails). Then, I can have that same host run a super lightweight SMTP server that can accept mails from the application, and send them on to recipients.
Almost crucially, I want this server to basically just run on localhost so that only this application can connect and send mails through it, but so that it can't really "receive" mails sent to my domain (I have set the MX priority very low (well, a high number) for this app server). I figure since I'm running my own SMTP server, that I don't really need to authenticate against it (it's running on localhost), just take in any mail and send it on to recipient domains.
When sending on to recipient domains... does the SMTP server need to authenticate to say, the gmail SMTP server as a user in order to send mails over there? That seems weird, since it's not a user logging into gmail to send mails, it's an SMTP server that is authorized within SPF sending mail from my domain (From address from my domain as well) to where ever the app server user's email is based (in this example, the user would be e.g., some_user#gmail.com).
I tried using python's aiosmtpd command-line and telnet to send a mail from test#MY_DOMAIN.TLD to test#MY_DOMAIN.TLD and it didn't seem to deliver the message; I figured aiosmtpd would connect to the preferred MX servers for my domain (my "real" MX's) to transfer the message, which would then put it in my inbox. That didn't seem to be the case, and I'm not sure why.
Exact repro steps, where example.com is my domain, and terminals are running on a box with a hostname listed in my MX records.
Terminal A:
$ aiosmtpd -n
Terminal B:
$ telnet localhost 8025
EHLO <example.com>
MAIL FROM: test#example.com
RCPT TO: test#example.com
DATA
FROM: Application Notifications <test#example.com>
TO: User Name <test#example.com>
SUBJECT: App Notify Test
This is a test!
.
QUIT
How do SMTP servers normally send mail between each other? Do they each get some login to each other's SMTP servers to authenticate with, and since I'm not doing that, this is a problem? Can I run a SMTP server on localhost and have it send mail out of the network without receiving mails (a no-reply service)? Is there something obvious that I'm just missing here that solves all my problems?
Thanks
It sounds like you want to run a mail transfer agent (MTA) that relays email to remote SMTP servers. An MTA will typically act as an SMTP server to receive messages, and then it will act as an SMTP client when it relays the messages to remote hosts.
MTAs generally operate in two different modes: (1) They will relay messages from authenticated users to remote hosts, and (2) they will receive messages from remote hosts to its users and store them somehow. The combination of those two modes - where the MTA will accept messages from remote hosts and relay them to different remote hosts - is called an open relay and is sure to attract spammers and place your server on spam blacklists.
aiosmtpd is not an MTA or an email relay out of the box - it is merely an SMTP server that will receive messages and do whatever with the messages you program it to do. By default it will do nothing - that is, it will receive the messages and throw them away. If you want to implement an email relay in aiosmtpd, then you need to implement the SMTP client portion of the MTA, e.g. by implementing an aiosmtpd handler that instantiates smtplib.SMTP to connect to remote hosts.
However, if all you want is an email relay, then you most likely don't need aiosmtpd at all - postfix is probably a better choice.
aiosmtpd can be a good choice if you need to implement mailing list software or perform some automation tasks based on incoming emails from e.g. cameras or scanners.
If you want to implement an email relay in aiosmtpd, then you need to ensure that both the software and your server are configured in a way that you don't relay unauthenticated messages from the outside internet.
See also: Python aiosmtpd - what is missing for an Mail-Transfer-Agent (MTA)?
So, I actually figured out what was missing here.
I need to run an SMTP server, yes, but I also needed to write code to parse the "to" domain (the recipient domain), perform a DNS request for the MX server(s) of the recipient domain, and then use the smtplib client to then send mail over to the recipient domain. Authentication is not needed to relay that message to the recipient server, authentication is only required for reading from a given inbox or authenticating a sender to send on behalf of a domain (I trust myself and myself only to send mail). I can do all this while also only listening for mail on localhost so that only my local server can use the local SMTP server for relaying messages/emails off to recipient domains.
Additionally, I don't need to have my external IP listed as an MX server since it's not accepting mail for the domain, only sending. I do need an SPF record for it though so that it is an authorized relay/sender for email from my domain.
I have a Coldfusion page (CF10) that creates a report and sends it via cfmail to a list of recipients. The ones in our internal domain are receiving, but the external addresses are not.
I found a couple threads where people were having the exact same problem, and the solution was to add the CF server's IP address to the Exchange server. So our IT guys did just that - they added the IP addresses of all of our production servers to the receive connector on the Exchange server. However, the mails are still not being relayed, and I'm continuing to get the same message in the mail log:
javax.mail.SendFailedException: Invalid Addresses; nested exception is: com.sun.mail.smtp.SMTPAddressFailedException: 550 5.7.1 Unable to relay
I'm not familiar with everything that needs to happen to make the Exchange Server relay email to external addresses. Adding the IP addresses to the receive connector obviously isn't enough. Are there other steps that need to be performed?
Coordinate with your IT guys. Write a ColdFusion page that they can run that sends mail to an external address they can access. Then tell them to do what they have to do to receive mail at that address.
Solution was simple - we originally specified the mail server in the cfadmin mail settings, but included no username/password. That worked fine, until we wanted to start sending cfmails to addresses outside of our own domain. So IT created a dedicated "Noreply" account for this purpose, and I entered the username/password in the cfadmin mail settings.
I am trying to send a mail from centos machine, but I came to a problem. I have installed "mail" and ssmtp inside my linux machine and I got this response when I try to send a mail.
ssmtp: 550 invalid DNS MX or A/AAAA resource record
FromLineOverride=YES
mailhub=smtp.1und1.de:587
UseSTARTTLS=YES
Of course, with the correct password and user.
I have tried already couple of users and everybody are returning the same.
I have tried even with my own user and the password that I have, but it won't work.
If you have any other approaches to this problem let me know also.
What am I doing wrong ?
The problem seems to be the FROM address for the SMTP envelope. Some SMTP servers will ignore an invalid value like Gmail for example (that's why it worked for me with Gmail) but if you're using 1und1 SMTP-Server you have to override the domain if it's not the same as the mail domain (e.g. if you're on a local test server).
You can override the domain in the /etc/ssmtp/ssmtp.conf:
Assuming your email is: my#yourdomain.de
rewriteDomain=yourdomain.de
We have a VPS with CentOS combined with DirectAdmin which we use for a Magento shop. This runs fine, except for sending email.
Problem:
It appears that some specific domains won't receive our emails and we get a bounce. If we use any other email sending systems, the mails arrive without problems.
The bounce mail contains the following error:
SMTP error from remote mail server after HELO Company-Shops:
host mx-cluster-b2.one.com [IP ADRESS]: 504 5.5.2 :
Helo command rejected: need fully-qualified hostname
After googling and trying things for a week now, I am a bit lost. I tried checking postfix in CentOS, but this is not installed and I'm not quite sure if this is needed.
Possible issue?
I believe the hostfile in CentOS is setup incorrectly:
127.0.0.1 localhost localhost.localdomain localhost4 ... etc
OUR IP Company-Shops
'Company-Shops' should probably be a domain name, am I right? The same as the rDNS. But I'm afraid if I change this it will kill my site and whatnot. I'm not sure if this entry correlates with the 'company-Shops' helo label in the bounce error.
Some extra info:
- We use the webmail Roundcube from DirectAdmin
- At the moment we run one shop, but this might grow a bit (multiple sites on 1 IP)
- We don't use subdomains
- We've set up a reverse DNS, with the domain
Is there anyone with similiar experiences or with a bit more knowledge about this subject? I appreciate any advice we can get, as we are stuck..
Many thanks.
Yes, that's right: your mail server should identify itself using a fully-qualified domain name when it connects to send mail via SMTP. You don't say what mail server you're running, but since you're using DA, it's probably Exim. If so, you want to edit /etc/exim.conf and set primary_hostname to the FQDN of your server.
This would also be a good time to double-check that reverse DNS is set up properly for your IP address. Many hosts will also reject email from servers on IPs without a valid rDNS record.
I'm not familiar with Magento, but I can't see any way that changing the Exim configuration in this way could impact that program.
Following Problem: I have written a mailing-list via PHP, SwiftMailer and Postfix. On my Old server it worked without any problems, but Since I moved to another Server (Exactly same configuration, but other IP) the list-mails stuck in the Spamfilter of the Receivers. (Espacially in Google Mail)
Is there anything I have to do escept rerouting the URL DNS-Records, that Google sees, that "I am that Server" and the mail is no spam?
First, check that your outgoing mail server is identifying itself correctly in the HELO command (or EHLO command) when it connects to a receiving mail server. There should also be an A record for this name that should point to the IP address of the mail server. Also, this IP address should reverse to some name (possibly, but not necessarily, the same name as above), and this name should point to the mail server's IP. If any of this is not right, then most spam filters will not consider your server to be a 'real' mail server, and will most likely flag any message sent from your server as spam. This is how many spam filters block spam that originates from computers that have been taken over as 'zombies'.
Another thing to do is to check that you mail server IP is not on any blacklists. You can use MXToolbox for this: http://mxtoolbox.com/blacklists.aspx
Another thing you can do is use port25's verifier tool. This tool will spot any red flags that might be causing your messages to be flagged as spam. See http://www.port25.com/support/authentication-center/email-verification/ for more info.
Last but not least, you might want to setup an SPF record for the domain that you are sending these messages from, to indicate that the IP of your mail server is authorized to send mail from this domain. This will help a lot. For more info, see: www.openspf.org.