Linked Questions

16
votes
2answers
3k 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
4answers
968 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 ...
20
votes
3answers
1k views

What are the best methods for catching snowshoe spam?

I'm using Smartermail for my small mailserver. We've been having a problem lately of getting waves of snowshoe spam that follow the same pattern. They come in batches of 3 or 4 at a time. The ...
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
6
votes
5answers
5k 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
1k 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 ...
2
votes
2answers
3k 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 ...
1
vote
2answers
864 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
1answer
2k 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 ...
0
votes
3answers
2k 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
411 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
2k 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
votes
2answers
774 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 ...
1
vote
2answers
554 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: ...
3
votes
1answer
154 views

Does postfix reject spoofed senders?

Is there a reliable way to reject incoming mails with a spoofed e-mail address? What kind of checks does postfix run normally on incoming mails? does postfix check the reverse dns by default? does ...

15 30 50 per page