I am trying to set up the most simple email server on an Amazon Linux 2 host for simple outbound mail (e.g. sending system messages). Following instructions on the net, I have installed mailx and sendmail. I am not committed to either package, I just want a simple setup with a minimal footprint. I have no problem switching to postfix if that is a better solution.
For configuration I have made the following changes.
/etc/sysconfig/sendmail:
DAEMON=no
/etc/mail/submit.cf (hostname obfuscated):
D{MTAHost}smtp.******.com
This works fine, and I am able to receive mail that is sent from the system.
There is a wrinkle. The anacron process is sending mail to the root account. However, rather than the mail being kept internal to the system it is being sent to the SMTP server. The SMTP server sends the message back to my host, which doesn't accept mail, and a loop is created when an 'undeliverable' message is send back to root on the host that doesn't accept mail.
How can I configure my system so email to root stays local and is not sent to the SMTP server? Any other 'best practices' suggestions would be welcome as well. And again, if switching to postfix is better, I am willing to do so (but will need configuration guidance).
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 question script for running forward my own email (do not have autoforward facility) to my Gmail. I want to do it using phpmailer.
So I can make cronjobs for running php script everyday (running get email and forwading to my Gmail).
How can I go forward with this?
PHPmailer alone will not be able to help you with forwarding as it is only a transfer class, for outgoing emails. You will need to set up a mail server (like Postfix) with an email handler (like Dovecot) if you are in Linux to receive incoming emails. PHPmailer can be used for the forwarding process but there are other solutions.
I recommend you look into a service like mailgun.com instead. They have a routing feature for forwarding incoming emails that is very easy to set up (if you have dns access to your current email domain). You can send 10k emails for free each month with the service.
I am developing custom features for osTicket and I need to setup a mail system that sends emails, locally, and can simulate several email inboxes.
My local development setup is vagrant with ubuntu precise 64. I already have the LAMP stack running.
osTicket needs to send emails (only internally) and needs to have mailboxes (osticket reads and processes incoming mail on selected mailboxes).
I installed postfix, but could not get it to work.
Thank You.
Recently, I installed osTicket for my company. It can allow you to setup SMTP, which can use your Gmail account to send email. It is simple to setup.
The only thing to keep in mind is you need to use "Allow less secure apps to access your account". See: https://support.google.com/accounts/answer/6010255?hl=en for more information.
Configure ssl://smtp.gmail.com as your SMTP address and port 465 as your SMTP port. Even if you are not using Gmail, you still have to put "ssl://" before your SMTP host name.
My VM-Ware VM running Debian 6 doesn't send emails since I moved to another house with another modem/router. I did a complete reinstall of Debian, but still I can't send email. My network adapter is set to 'Bridged' (with 'Replicate physical network connection state' enabled).
I installed an application that needs to send an email to work properly. But I can't finish it because I don't receive an email at all.
date | mail test#example.com on the command-line also doesn't work, so it hasn't something to do with the application.
Do I need to configure my router in order to send external emails from my VM?
I managed to solve the mailing-problems!
I needed to do two things:
Setting up a SMTP-server for Postfix because my ISP doesn't allow usage of port 25 without using their SMTP-server. See this reference for a how-to.
Then I needed to configure a 'send-from adress', because by default emails are sent from a localhost email adress. The SMTP-server doesn't recognizes this as valid and prevents the email from being sent. See this reference for a how-to.
It cost me almost a few days to solve it, but now I can receive outgoing emails from my Debian system :).