Questions tagged [postfix]

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Dealing with particular clients wrt TLS support in postfix?

External (other) Mail clients have started to deny/de-list anonymous ciphersuites. But the TLS support is often spotty. Worse, some clients (mainly Windows, which does not care one whit about your RFC ...
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  • 273
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2 answers
217 views

My postfix server is getting DOSed, what can I do?

Port 25 is open and I'm getting thousands of emails. How can I make it stop?
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  • 461
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Unrecognized mails sent from my mail server - please help to find the "hole"

Since about 2 weeks, I am receiving from time to time (about 2-3 times per week) similar emails: What do I have: A VPS (webserver) with Wordpress, configured to send emails via SMTP, thanks to the ...
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  • 101
-1 votes
1 answer
1k views

Unauthorized access postfix "lost connection after MAIL from unknown[127.0.0.1] " [closed]

Someone or "something" is trying to access the server. my postfix log showed: mx2 postfix/smtpd[*****]: lost connection after MAIL from unknown[127.0.0.1] My concern is why is it from the ...
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  • 13
1 vote
1 answer
180 views

Postfix pickup daemon "from:" verification

I was surprised to notice that sending email from a local server account allows any user to send a message with: From: whatever@whateverdomain This is a security issue, because it allows identity ...
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1 vote
3 answers
727 views

POST requests are bypassing PHP checks

I have a website with a contact form on PHP and a mail server. Email are sent with the help of PHP mail function like so $name = cleanInput($_POST["name"]); $e = $_POST["email"]; $email = filter_var(...
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  • 113
2 votes
2 answers
2k views

DMARC report for mails I didn't send

I set up DKIM, DMARC and SPF on my domain/server a few years ago, and never touched it again since then. Here are my DNS records (my domain is mydomain.com and my IP addresses are 1.1.1.1 and 2001::1)...
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  • 23
68 votes
1 answer
12k views

Unusual mail headers show evidence of MTA attack. Have I been pwned?

Today I found an extremely unusual email in my catchall inbox, without subject, sender or content. My Gmail client for android reported the mail was sent by me, triggering a nuclear alert in my mind. ...
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1 vote
1 answer
493 views

Postfix SMTP - Can I use SSH public keys instead of sasl password

I am relatively new to managing mail server, although i am familiar with webhosting servers not running dedicated email services. Postfix is configured to use sasl-password authentication I have ...
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  • 13
3 votes
1 answer
318 views

Why are my emails going to spam?

I have been trying to learn about phishing emails. I have read up quite a bit on it. I setup a domain somthing.tk (free domain), hosted a website on a VPS (Digital Ocean). Set up my own mail transfer ...
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spam that penetrated reject_sender_login_mismatch in postfix

We have the following in postfix's main.cf: smtpd_recipient_restrictions= permit_sasl_authenticated, permit_mynetworks ... smtpd_sender_restrictions = permit_mynetworks, reject_sender_login_mismatch ....
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Is `tls_preempt_cipherlist = yes` in postfix a good idea nowadays?

Postfix' own documentation says it may cause issues, but only mentions "Windows 2003 Microsoft Exchange clients". Everything else I've found (first was CheckTLS, as far as I've been able to find, that'...
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2 votes
1 answer
4k views

Is TLS 1.3 supported in Dovecot 2.3.4 and Postfix 3.3.2?

I would like to configure an email CentOS 7-based server to use TLS 1.3. Currently it uses TLS 1.2 for securing the SMTP and POP3 sessions. For SMTP I use Postfix software and for POP3 I use Dovecot ...
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0 votes
1 answer
168 views

Linking mail server with application database

I have a web application running on node.js, backed by a MongoDB database which stores user data etc... I'd like to offer my users an email account, so I've set up a mail server using Postfix, dovecot,...
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  • 143
3 votes
1 answer
3k views

How should output of fail2ban postfix-sasl look like

I want to be sure that fail2ban is properly banning failed postfix SASL login attempts. When I do iptables -L I can see list of banned hosts for SSHD, but I can't figure out a way to see banned ...
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-1 votes
1 answer
384 views

What is the most secure communication between firewall, and DMZ

I have 2 virtual machines. (Vmware esxi 6) They are both opensuse 42.3 (tumbleweed) Firewall (iptables,ipset,dhcpd,dns only) mail/web server. (apache,dovecot,postfix) The web server can not ...
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  • 518