Linked Questions

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0answers
26 views

SMTP Postfix server probably used as a spam relay : how to protect? [duplicate]

I'm using my own mail server to send and receive emails : a Debian 6.0.7 running Postfix 2.7.1 and Courier. Today, I'm suspecting that this server is used as a SMTP relay for spammers... The clues are ...
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votes
2answers
120 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
2answers
70 views

Many invalid HELO from

I've been recieving many invalid helo requests from a Microsoft domain. I already did send a question about this but they still do not respond. maillog: Jan 14 19:27:14 relay postfix/smtpd[57104]: ...
1
vote
0answers
42 views

How to professionally handle spam / abuse complaints as an ISP [closed]

Introduction story to have a base and not some sort of meta-question I am handling some spam cases where our email addresses got bought or collected somehow by some marketing agencies, from which we ...
15
votes
5answers
353 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 ...
6
votes
4answers
500 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 ...
-1
votes
1answer
156 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 ...
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votes
1answer
345 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 ...
1
vote
2answers
213 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: ...
1
vote
1answer
748 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 ...
2
votes
3answers
577 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 ...
0
votes
1answer
146 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 ...
0
votes
4answers
303 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 ...
2
votes
2answers
1k 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 ...

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