Linked Questions

66
votes
9answers
21k views

How to stop people from using my domain to send spam? [duplicate]

I receive Mailer Daemon messages saying certain emails fail. My domain is itaccess.org which is administered by Google apps. Is there any way I can identify who is sending emails from my domain, and ...
2
votes
3answers
913 views

Should I reject email on SPF and/or DKIM failures? [duplicate]

I’m administering a mail server (cPanel/WHM) running Exim. It handles normally a few hundreds incoming emails per day for our customers. I’m not sure if I should reject SPF and/or DKIM failures for ...
-1
votes
1answer
675 views

Suddenly Gmail and Hotmail block our emails [duplicate]

Starting from yesterday, all emails sent from our server are being rejected by Gmail and Hotmail. Everything was working properly until now. Here are the error messages received: Gmail Failed ...
0
votes
2answers
198 views

DKIM, spam probability, signing with key at mail server vs sender domain? [duplicate]

I'm working on an email marketing tool and so far we've been recommending our customers to set up an SPF-record (Sender-ID) and a DKIM-record, we also have our own SPF-record on the mail server and a ...
0
votes
4answers
371 views

Stopping incoming spam with sendmail [duplicate]

I am having an issue due to a "smart" sysadmin that made some choices while I was away for two months: Spam. I manage probably close to 10,000 web/mail sites. He decided to allow all mail to ...
-1
votes
1answer
315 views

sendmail - Server Sending Spam? [duplicate]

for the past day my server is being used to send a spam. I'm using the Amazon Linux Distro (RedHat based). It has sendmail 8.14.4. It is setup to require authentication, SSL etc. Below are some ...
0
votes
1answer
83 views

Project Honeypot says my mail server has become a spammer [duplicate]

I need help diagnosing this: http://www.projecthoneypot.org/ip_66.18.204.186 It says my server has been sending spam for 4 months! I try to be a responsible mail server admin, I hate spam, I do ...
-1
votes
0answers
46 views

CBL listed me blacklisted [duplicate]

Server: Dedicated OS: CentOS 6.5 MTA: Postfix Open Relay: None I've been fighting this blacklisting for a week. CBL says: IP Address xxx.xxx.xxx.20 is listed in the CBL. It appears to be ...
-4
votes
1answer
30 views

No way to create an effective spam filter [duplicate]

We are having a big spam problem and we don't know how to resolve it. We have one spammer that send us mail daily. All these emails are from different themes, using different email addresses that are ...
34
votes
4answers
3k views

Is greylisting still an efficient method for preventing spam?

I've used greylisting on my servers for many years, but I don't know how effective it is nowadays. Is it still good for fighting spam in 2012? Or is the typical spammer MTA capable of resending ...
6
votes
4answers
690 views

How can I block outside mail FROM postmaster@mydomain.com?

A security firm has been testing my mail server and claims my Postfix daemon is an open relay. The evidence is as follows (valid public IP for mail.mydomain.com has been changed to 10.1.1.1 for ...
16
votes
5answers
385 views

Is it good practice or too draconian to reject mails from mailservers with no RDNS

I've recently dropped SpamAssassin and am now basing spam rejection on DNSRBL's, grey-listing and other basic tests and I'm wondering whether I should also block hosts that don't have a valid RDNS ...
9
votes
2answers
2k views

What are SPF records, and how do I configure them?

This is a canonical question about setting up SPF records. I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer ...
6
votes
6answers
2k views

Spam prevention tips for Postfix

Without using SpamAssasin, or similar, what are your best tips for preventing spam. Please try and provide config examples :D
5
votes
5answers
4k views

Is there any alternative to SpamAssassin? [closed]

I'm looking for alternative to spamassassin. Anyone tried rspamd from Rambler.ru (https://bitbucket.org/vstakhov/rspamd/wiki/Home)?
4
votes
6answers
789 views

Prevent outgoing spam

What are some ways to prevent spam from leaving your servers should a hosting account get compromised? Have a bunch of clients on a server with cpanel but wondering if there was a way to just ...
1
vote
2answers
632 views

Spam mail through SMTP and user spoofing [closed]

I have noticed that it's possible to telnet into a mailserver that I own and send spoofed messages to other clients. This only works for the domain that the mail server is regarding; I cannot do it ...
2
votes
2answers
2k views

In postfix, how to enforce tls + auth over 587 while leaving tls optional for 25

I would like to host mail services for some domains. I have succesfully setup postfix to consult sql for those virtual domains. What I would like to do is: For connections on 25: 1. Deny relaying ...
0
votes
3answers
1k views

smtpd_helo_restrictions = …, reject_unknown_helo_hostname occasionally rejects mail I care about, how to handle?

I have configured my postfix as follows: smtpd_helo_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unknown_helo_hostname This is working well because most spambots don't seem ...
-1
votes
1answer
306 views

Hotmail blocks company emails, when hyperlink is inserted in the message body [closed]

I received the following results: ========================================================== Summary of Results ========================================================== SPF check: pass ...
0
votes
2answers
1k views

Receiving spam where sender is @mydomain [duplicate]

Possible Duplicate: How to stop people from using my domain to send spam? I am running a mail server with Ubuntu + Postfix + Maia Mailguard + Dovecot, all has been working well until ...
1
vote
1answer
1k views

Cloudflare, reverse DNS and php mail ending up in spam folder

I've been using Cloudflare to host my DNS, and PHPMailer to send e-mail through ZOHOs SMTP servers with great success, but have found that all my e-mails are hitting Gmail, Zoho and Hotmails spam ...
-1
votes
1answer
871 views

Configuring postfix to fight spam, 2012 edition [closed]

EDIT: This question was poorly asked, later I found another question which answers what i wanted to know: Spam prevention tips for Postfix I'm running a small (20 users, 30 mailman-lists) server with ...
1
vote
2answers
317 views

Postfix - unable to access externally

So I can't seem to access smtp from externally. When using a desktop email client (eM client and thunderbird both fail) I can't get it to hit the server at all. (eM client is trying to hit: ...
5
votes
1answer
229 views

How to use two mail servers in parallel, if possible?

I basically want to have two separate email servers. The first one is the GoogleApps GMail service, which is for humans to use. The second server would be for sending messages from my application (so, ...
-7
votes
2answers
536 views

Mail server not sending or receiving after removal from barracuda blacklist to white list [duplicate]

Possible Duplicate: mail loops back to myself | postfix Mail server not sending or receiving after removal from barracuda blacklist to white list. I've checked against black lists and the ...
-1
votes
2answers
211 views

Postfix is Sending Spam [duplicate]

I have an Ubuntu 12.04 server, hosted on AWS, that powers a dozen WordPress installations using Nginx and php5-fpm. The problem just began one day. My server was down. Panic! Whenever I turned it on ...
0
votes
1answer
180 views

IIS6 SMTP server retrying too fast (after 451 greylist)

I have my IIS6 SMTP server with default retry settings of 15 min, 30 min, etc. but under some circumstances it keeps retrying every minute (or less). How can I fix this? I have seen it retry ...

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