30
votes
2answers
8k 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 ...
-1
votes
2answers
148 views

How can I reject spam before reaching SMTP on Postfix

My server has started receiving thousands of attempts to use my mail server to send spam from dynamic.hinet.net. The attempts are always rejected, but it's non-stop. I'd like to block these attempts ...
11
votes
3answers
3k views

Prevent mail being marked as spam

This is a canonical question about avoiding outgoing mail being classified as spam. Also related: Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User? What ...
2
votes
1answer
84 views

Why are messages queued and not sent with sendmail?

I am having trouble with one of my sendmail servers. Users are informing me about that registration emails do not arrive. The logfile claims that the message has been queued, but the queue is empty: ...
0
votes
0answers
22 views

Emails ending up in gmail spam folder [duplicate]

Emails from my dedicated server are ending up in spam folder in gmail even though the server is not blacklisted and with good reputation - see below. the server level issues that would cause this ...
1
vote
2answers
50 views

How to find out who is sending email

I have a server which doesn't have much activity. Today, suddenly server load went higher than 12 which compared to its normal value(0.5) is way too high. I checked and found out that postfix is being ...
0
votes
2answers
62 views

How reliable is validating email domain by reverse DNS MX record checking [duplicate]

This question is not about how to protect against spam or validate a particular email user. But how reliable is validating emails domain (does it exists at all) by reverse dns. What are the pitfalls ...
0
votes
2answers
48 views

How do IPs end up on the spam blacklists

I don't know if this is the right place to ask this kind of question but here goes. I have 3 IPs on my server, which I'm running for shared hosting. The main shared IP gets blacklisted sometimes, ...
0
votes
0answers
24 views

postfix filter “Do you want to have more lovers?” [duplicate]

My postfix is currently set up to check email content and reject by keywords. However, I can't think of a good way to block this kind of emails: Return-Path: <gievcyopa@beamtele.com> ...
0
votes
1answer
35 views

How to prevent spammers sending bogus@mydomain emails out of my name [duplicate]

Lately I receive a lot of Delivery Status Notification (Failure) e-mails. Bogus spam email is sent from blablaxx@mydomain to other emailadresses, and bounce back to my catch-all info@mydomain with ...
7
votes
2answers
8k 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: Deny relaying ...
-1
votes
1answer
49 views

How to improve spam protection using postfix? [duplicate]

I try to improve the spam protection of my postfix install for several weeks now, but I still receive spam. What I've done so far: Added SpamAssassin Added SPF record Tuned rejection rules Now ...
0
votes
4answers
4k 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 ...
-2
votes
2answers
79 views

Mitigating spam on Linux server where all MTA's (Postifix, PHP Mail() function) etc. are disabled [duplicate]

We have a Debian Squeeze server running a fairly standard LAMP stack (back in the days it was set up using the Perfect Server guide at Howtoforge, so we're using ISPConfig as our backend admin panel) ...
1
vote
2answers
1k views

Helo command rejected: Host not found - Setup postfix to accept sending mails from my home server through my public server

I would like to receive system emails from my home server. So I'm trying to configure postfix to do that through my public server. My public server has a fixed IP, while my home server is in a private ...

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