Linked Questions

111 votes
9 answers
140k 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 ...
Billy Moon's user avatar
  • 1,437
98 votes
8 answers
196k views

How to send emails and avoid them being classified as spam?

This is a canonical question about how to handle email sent from your server being misclassified as spam. For additional information you may find these similar questions helpful: Best ...
kcode's user avatar
  • 1,835
60 votes
2 answers
24k 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 ...
vulgarbulgar's user avatar
54 votes
5 answers
13k 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 ...
neu242's user avatar
  • 724
30 votes
4 answers
12k 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 ...
jonepatr's user avatar
  • 405
21 votes
5 answers
3k 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 ...
Peter White's user avatar
21 votes
4 answers
3k 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 ...
pooter03's user avatar
  • 436
13 votes
5 answers
12k views

Is there any alternative to SpamAssassin? [closed]

I'm looking for an alternative to Spamassassin. Anyone tried rspamd ?
dynax60's user avatar
  • 139
12 votes
2 answers
36k 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 (...
Paralife's user avatar
  • 329
11 votes
3 answers
49k 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 ...
The Quantum Physicist's user avatar
7 votes
6 answers
5k views

Spam prevention tips for Postfix [duplicate]

Without using SpamAssasin, or similar, what are your best tips for preventing spam. Please try and provide config examples :D
Mez's user avatar
  • 457
7 votes
1 answer
8k 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 ...
lszrh's user avatar
  • 683
6 votes
4 answers
4k views

How can I block outside mail FROM [email protected]?

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 ...
sventechie's user avatar
6 votes
4 answers
12k views

Is it possible to find a list of all DKIM keys for a domain?

a DKIM-record is identified by its selector, which might be default, dkim or something else alltogether (and there might be multiple). When making sure that an e-mail's content is valid, the DKIM ...
Qqwy's user avatar
  • 159
6 votes
1 answer
20k views

Significance of NOQUEUE: reject: RCPT in Postfix log?

I set up brand new Postfix server last night and did not configure at all yet, just did the install. So, I logged in this morning to finish the configuration and notice that there is stuff in the log: ...
Tyler Durden's user avatar
6 votes
2 answers
1k 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, ...
omninonsense's user avatar
6 votes
1 answer
35k 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: ...
merlin's user avatar
  • 2,172
5 votes
6 answers
3k 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 ...
Nikki Wilson's user avatar
5 votes
1 answer
168 views

Blocking, filtering or reducing "tabloid" spam (emails that bypass Spam Assasin)?

In the past few weeks, we've been hit hard by a new class of spam email (or at least new to me/us). I'm calling it "tabloid spam" because they send supermarket-tabloid headlines with tabloid copy, ...
Nick's user avatar
  • 4,656
4 votes
1 answer
431 views

SPF - how is it useful if the receiver only verifies the MAIL FROM address?

If I understand correctly, the email receiver checks the validity of the origin of the email by matching the domain's IP of the MAIL FROM (Return-Path) address with the IPs listed in the domain's SPF ...
user2923322's user avatar
4 votes
1 answer
6k 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 ...
Joseph Szymborski's user avatar
2 votes
2 answers
6k views

DNS and SPF configuration for Microsoft Exchange

We've started receiving spam with spoofed addresses from our own domain. So I'm trying to get my PTR and SPF records etc correct to prevent it. We're running Exchange 2010 on site with one server ...
Daniel's user avatar
  • 253
2 votes
2 answers
811 views

Symantec adds email server IP address to blacklist without any proof - how to fight them?

Recently noticed that email server IP address 88.119.185.129 is added to Symantec email blacklist. This IP is clean, not listed at any blacklists. The email server is not open relay, all emails are ...
Ernestas Gruodis's user avatar
2 votes
3 answers
8k 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 ...
esc1729's user avatar
  • 305
2 votes
1 answer
920 views

DKIM Key Rotation Best Practices

Do you find it necessary to regenerate your DKIM keys every 1-6 months to avoid your mail going into the receiving servers' junk mail folder? Some guides recommend this, some even say it's "Best ...
Jeff's user avatar
  • 1,426
2 votes
1 answer
64 views

Sane Spam Strategy [closed]

Right now I'm using spamd to score spam and then procmail to put it in user's .Spam Maildir folder and then manually running sa-learn on .LearnAsSpam and .LearnAsHam and then also manually just ...
squarewav's user avatar
  • 140
2 votes
2 answers
12k views

Email/Exchange/Office 365 - Postmaster Spam

I use Office 365 for email with about 30 people using 6 domains. I occasionally receive messages from the "Postmaster" saying that an email was rejected which was never sent. For instance: ...
William's user avatar
  • 363
1 vote
4 answers
3k views

Prevent spamming [duplicate]

How to prevent spamming in Cpanel / Linux server ?
nitin's user avatar
  • 2,599
1 vote
2 answers
4k 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 ...
user avatar
1 vote
4 answers
10k 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 to ...
lkraav's user avatar
  • 786
1 vote
1 answer
2k views

Postfix forwards to Gmail being rate limited even with unmodified headers

I've installed Postfix on Ubuntu 14.04 with the defaults. I then configured some virtual aliases to forward email from a few addresses to various personal (mostly Gmail) accounts. This is just to make ...
David Rahrer's user avatar
1 vote
2 answers
3k 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: smtp://xxx@...
Aram Papazian's user avatar
1 vote
1 answer
3k views

emails to Yahoo are ending up in SPAM folder despite spf=pass, dkim=pass and dmarc=pass

Are we possibility having a reputation problems with Yahoo emails? Yahoo raw mail header finds my policy I published: dmarc=success(p=REJECT,sp=REJECT) Emails to clients at Google and Outlook are not ...
MeSo2's user avatar
  • 274
1 vote
1 answer
1k views

Emails sent with postfix treated as spam, and sometimes not delivered at all

I'm trying to set up sending emails with SMTP on my VPS running Ubuntu 18.04. I'm using postfix, nodemailer. When I send from an [email protected], to a gmail account, it gets stuck in the gmail ...
Joseph's user avatar
  • 135
1 vote
0 answers
348 views

Set Postfix to require authentication to send to own domain from own domain

My postfix setup (running in the cloud) successfully prevents relaying, requiring authentication to send to a non-local domain. However, spammers are sending to [email protected] from someotheruser@...
TSG's user avatar
  • 1,852
1 vote
0 answers
986 views

mail ends in google spam folder while SPF pass, DKIM pass, DMARC pass

I am trying to send basic mail to a gmail user test and the mail ends up in the spam folder. I don't really understand why. I used to send through ubuntu sendmail, spent a lot of time setting up ...
user1998000's user avatar
0 votes
1 answer
56 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 ...
Janghou's user avatar
  • 505
0 votes
2 answers
789 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 ...
Andreas's user avatar
  • 111
0 votes
1 answer
417 views

Got an Abuse email for spam from my server, but postfix logs don't show them [duplicate]

We have a server with 300+ websites on it, and it has gotten an abuse letter from spamcop. We have investigated the logs, and searched for the PHPMailer version stated in the mail and all came up with ...
Sniffleh's user avatar
  • 181
0 votes
1 answer
2k views

How to set postfix to just ignore mail to nonexistent users

I'm getting a huge amount of spamming attempts to random usernames. I know that it happens to all mail servers to some degree, but during the last two weeks there was so much that my VPS's disk ...
OsakaWebbie's user avatar
0 votes
1 answer
210 views

How to make a mail server spam "proof"

I work for a German company that sends several thousand emails to our customers every day. Our employees send their emails via Microsoft 356, but the system does not use a mail server and sends emails ...
Pa0x43's user avatar
  • 5
0 votes
1 answer
311 views

Fixing a server that has been listed an Email Spam [duplicate]

Full Disclosure: Setup of email servers is something fairly new to me, so go easy on me :) Recently users reported that they were not receiving emails from my site. The site runs a vbulletin forum so ...
MrEyes's user avatar
  • 313
0 votes
1 answer
6k views

Identifying source of spam/malware emails apparently from Office 365 user

An office 365 user discovered that around 100 emails were sent apparently from him; they have some kind of malicious PDF attachment. The message headers show "Received: from XXX.XXX.PROD.OUTLOOK.COM" ...
timanderson's user avatar
0 votes
2 answers
419 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 ...
undone's user avatar
  • 177
0 votes
2 answers
2k 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 ...
Ssss Ppppp's user avatar
0 votes
1 answer
396 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 ...
cecilkorik's user avatar
0 votes
2 answers
110 views

Email with different domain name are being sent from inside the organization to outside mail [closed]

Recently our domain was flagged as spam, and we found out that emails with spam are being sent from inside our organization but with domain different than our Domain. Example: our domain : email@...
IL876ANI's user avatar
0 votes
2 answers
42 views

Getting all internet domains a user owns

Is it possible to find out which other domains a user has registered? my company is atm recieving a lot of spam mail and the sender just buys a new domain and keeps spamming, so i wanted to know if i ...
Mathias Rønnow Nørtoft's user avatar
0 votes
1 answer
677 views

can someone explain this exim mainlog lines? [duplicate]

i dont understand this lines in exim mainlog , may anybody explain this ? my server is sending spam and i need to stop it. 2015-04-25 07:51:42 1Ylqf0-0000TF-G1 DKIM: d=mandrillapp.com s=mandrill c=...
Ehsan Chavoshi's user avatar
0 votes
2 answers
2k views

How to block IP addresses from port 25 [closed]

PROBLEM: Users are getting 15-20 SPAM emails per hour, even with SpamAssassin set to its most aggressive settings SOLUTION: SPAM filtering services are available from companies like McAfee (Intel). ...
DigitalSky's user avatar

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