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0

If you don't want to reveal your public IP you can't have any DNS recording pointing to it. Sounds like you set up an A record, which isn't required, you just needed an MX record. Suggest you remove the A record and sign up for hosted email, Google or FastMail are good options, but there are plenty. Point your MX record at the hosted email, and set up SPF as ...


0

The only requirement for incoming email is that you have an MX record that is an A record. That MX record could be any hostname, and it doesn't even have to be a subdomain of your domain. So, there's no problem with using abc.example.com. With regard to the website showing when accessed by mail.example.com, that really depends on how you have your webserver ...


3

That remote domain has an MX record pointing to the loopback address 127.0.0.1 which is either a misconfiguration by the owner of that domain or it's by design. We don't know of any really good reasons to do so: Under what circumstances (if any) should an MX record point to localhost? Either way that makes it impossible to deliver email to them. There is ...


2

99% of the time, email is delivered via the MX record mechanism. The MX record designates which server is authoritatively responsible for accepting email for a given domain. But that doesn't mean that this server is also the server where the recipients mailbox is. The MX record only designates which server to deliver the email to, it doesn't designate which ...


2

This statement is not accurate: " Email delivery is done by Sender's Mail Server sending E-Mail directly to Receiptent's Domain Mail-Server" For example, at my firm, when I send an email from my mail client, I might not have an externally-facing SMTP server at my site. Mail might be routed within my company's Exchange infrastructure. Then, it might ...


0

This is an interesting scenario. I have a few of these groups setup, and no special configuration was required. They seem to be routed and delivered according to MX records. Are the recipients added as mail contacts inside Exchange? It may also be something with the send connector. I know for local Exchange 2013/2016, you have to grant extended ...


0

you can use some network sniffer tools which will pinpoint to process level which one is sending what. You can as well filter if needed. some examples: network monitor 3.4 (microsoft) outdated, but works well. fiddler ... (other most probably) Give network monitor a try and within 15 minutes you know where to look next.


1

netstat -b -o lists the network connections, process and PID - you should be able to figure out which IIS worker process is doing all the port 25 connections.


1

Honest advice, use normal user accounts and let your Linux system authenticate the users. This is easy to manage and very secure. I don't want to say that other systems are insecure but I trust my Linux system when it comes to storing and authenticating passwords. I use these commands to create users manually. This way they can do no harm on my system. ...


1

if you want all the emails being sent via gmail, you have to set relayhost to smtp.gmail.com:587 as you wrote. This is not enough, though. You need to create and edit the file /etc/postfix/sasl_passwd Write a line in it like below: smtp.gmail.com:587 user@example.com:password where: user@example.com is a valid username in your gmail hosted domain ...


0

I left the idea of using postfix and dovecot and simply installed sendmail to achieve it.


1

SSMTP is expected to be TLS from the start. This should work if you set UseTLS to Yes. This port/protocol has been obsoleted now that the STARTTLS option is available. If you want to use STARTTLS try the submission port (587). I have verified that the submission port is open.


0

I don't suspect this to be a DNS caching issue. In your case, this is a brand new MX record and A record so there shouldn't be any DNS caching involved. What is probably the cause of the problem is that you haven't created an Accepted Domain and Recipient Policy in Exchange for the domain in question. I would look there as the root of your issue.


-1

You are likely to require a reverse DNS entry before anyone will trust your server to exchange emails with them. In addition, more mail servers are requiring encryption using TLS. Also some will require SPF and possibly DKIM. Your DNS records will normally propagate within an hour or so but can take 48hrs to propagate worldwide.


0

Thanks to @ychaouche I found the solution. The client-side did not accept the certificate. Which means the SSL transmission was not allowed. After restarting client-site mail-application and trusting this untrusted openssl cert everything worked as expected! Thanks!


3

When I format the smtpd_sender_restrictions so it becomes a little more readable: smtpd_sender_restrictions = reject_unknown_sender_domain, reject_unauthenticated_sender_login_mismatch, reject_known_sender_login_mismatch, hash:/var/spool/postfix/plesk/blacklists, ...


1

Most people use MX or A in their SPF record that covers all of your MX Records and A Records v=spf1 mx a -all If you're not sending from your MX records then you can list out the ip4 addresses you send from. The best way to create your SPF Record, if you're not sure is to use an SPF Wizard You'll go through the questionnaire and it will produce the ...


1

If you just have those two IP-addresses sending mail for the mydomain.com domain, your SPF record should look like this: v=spf1 ip4:1.1.1.1 ip4:2.2.2.2 -all Do not use +all in a SPF record, since that allow the whole internet to send mail from your domain. In the final SPF record you should use -all to indicate that ONLY the listed entries are allowed to ...


1

The RFCs generally recommend a limit of 100 recipient addresses per message. The mail server may expand this list if a recipient is a list known to the server. This applies to the envelope recipients, not the recipients listed on the header. For a mailing lists, it is bad practice to list the recipients unless the message is being sent to a single user, ...


0

Incorrect access restriction to the service. Its the step 6 of your tutorial. If its setup correctly be sure you have no antivirus that scan/restrict the port 25. It can cause such issue too.


0

The question you might want to ask yourself, is what is the benefit in knowing what script sent the email? Certainly you should be looking to fix your security, but the exploit is not the same thing as the vulnerability - there are multiple things an attacker might do with your system, not just sending email. So really your focus should be on fixing the ...


0

Did you check web log? Try to look process with ps to identify process which sending spam. Maybe you can catch it there. Second, maybe spammer periodically send by crontab, check every crontab in your system to identified the bogus script. –°heck one of the email with postcat to see which script tries to send them: postcat /var/spool/postfix/deferred/1/{$...


4

Damn it. I fixed it like a min after posting this. Solution: echo 1 > /proc/sys/net/ipv4/ip_forward


3

SPF checks occur early on in the conversation so the sender (probably) doesn't get a chance to send the email before the attempt is rejected. So no, they're not recoverable.


0

I think you may want to modify your sql select statement to be sql_select: SELECT password FROM mailbox WHERE username='%u@%r' AND active ='1' as that should select both the user and domain..


0

Emails started going out as soon as I replaced postfix with sendmail. Additional configuration may be appropriate, but my site has passed the smoke test.


1

Inbound options do not apply to PHPMailer. SSL on port 465 (SMTPS) has been deprecated since 1998, though Microsoft didn't seem to notice. Use SMTP+STARTTLS on port 587 instead, which is what PHPMailer does when you use SMTPSecure = 'tls' & Port = 587. Note that PHPMailer does opportunistic TLS, in that if you don't tell it to use TLS and you connect to ...


2

Note that it's 250 8BITMIME and not 250-8BITMIME (with the dash). Would this be enough for sendmail to consider that the remote source doesn't support 8bitmime? No. This is called continuation and it only signifies that the line is the last line of the SMTP reply. And generally 8BITMIME should be the only thing required to show that the MTA on the ...


4

I hate to turn this into a discussion about tools, rather than about the technology involved, but you may want to look into the use of tcpreplay which takes .pcap files and replays them even at the same speed that they originally came in.


1

I think the problem is here #mynetworks = 168.100.189.0/28, 127.0.0.0/8 Try to add and network 192.168.178.0/24 and del # mynetworks = 127.0.0.0/8, 192.168.178.0/24


0

smtpd_sasl_auth_enable = yes is required. (not smtp_sasl_auth_enable) Perhaps, it may be necessary to change the order of smtpd_recipient_restrictions. smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, (other reject rules)


3

I'm going to assume that you have looked into running multiple postfix instances? There are variations you could do (this for example), but they'll involve using the different IPs with different domain names (so you can assign SSL certs to them), and either running one instance which submit internally to different ports in amavisd, then re-injects to ...


1

Sendmail had used to be installed as set root uid program. Sendmail-8.12+ is no longer (by default) installed as set root uid program to avoid security risk. Sendmail executed by non root user passes messages to sendmail daemon running with root privileges at 127.0.0.1:25. Sendmail executed by non root user uses /etc/mail/submit.cf instead of /etc/mail/...


1

Quite a good one, it requires fiddling with zimbra and postfix and unfortunately requires some manual configuration. I suppose you can handle the amazon stuff for getting an account. all commands are done on the cli as the zimbra user. So login with ssh and become zimbra user by su - zimbra create an file for authentication to amazon: echo email-smtp.eu-...



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