0
votes
1answer
19 views

SMTP Headers Guide [closed]

Is there a guide/cheat sheet that explains Email/SMTP headers in detail? I could not find any useful resources after plenty of Googling. The purpose is to understand the headers in order to be able ...
1
vote
1answer
97 views

Postfix is Sending Spam [closed]

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
0answers
95 views

SMTP blocking a legit email, no way to contact yahoo or anyone about it?

Very frequently, I have trouble emailing from Yahoo to people with their own domain. For example, when I send an email from myname@yahoo.com to someoneelse@theirowndomain.com, I'm getting a bounce ...
1
vote
1answer
141 views

Do spam filters block emails whose 'from' field's domain is different from SMTP server domain?

Consider an email sent from smtp.eumx.net: From: "John William" <john.wm@inter7.jp> Reply-To: john.wm@inter7.jp To: foobar@yahoo.com Cc: peter@gmail.com, mary@gmail.com, ... Note that the ...
1
vote
2answers
435 views

Can a virus send mail from my computer if I don't have Outlook?

My ISP does not allow SMTP port 25 connections outside its network but only port 587. I don't use a desktop mail client like Outlook. Can a virus still send spam mail from my computer? How?
2
votes
1answer
878 views

Securing smtp with login

I have a ispconfig server, and it seems that someone is using it to send spam. I got about 130 "Mail Delivery System" email about declined send email. This spammer uses my email address as sent from ...
3
votes
1answer
271 views

ISP mail server blocking me?

I'm currently writing an email client for fun/practice and I've noticed that after sending out a handful of test emails (10 or so) over a short period of time, the emails stop going through. At some ...
0
votes
1answer
42 views

Microsoft Excange antispam forges

Could someone please tell me about How MS Exchange fights against spam. I have experienced Mdaemon server setup. It could use DNS records checks (existance of ptr record, accordination of peer ip ...
3
votes
5answers
9k views

How can I find a computer on my network that is doing mass mailings?

I was notified by my isp that one of my machines is sending out spam. This happened about 3 months ago on windows machine running cygwin that was hacked due to an SSH vuln. The hackers setup IIS and ...