32
votes
Does DKIM alone not solve the spam issue? Why do I need SPF?
SPF and DKIM are protecting different things altogether: SPF protects the envelope sender whereas DKIM protects the integrity and authenticity of email headers and body. Furthermore, DKIM can only ...
- 49.8k
29
votes
Accepted
Spam emails regarding Domain Abuse Notices
This is spam at the least - at worst, it's a scam. Do not agree to send a read receipt. Do not download unnecessary content. Do not click links. Do not reply. Do not pass Go... etc.
As others have ...
- 410
23
votes
How do I check a PTR record?
I know this has been marked as answered but I want to provide a more comprehensive answer. For my examples I will be using:
google.com's IP address 172.217.3.206 because it does have a
PTR record.
...
23
votes
Accepted
Automated telephone call about sending spam mails
That is not a normal way to report spam. In fact, it's utterly bizarre.
The generally accepted way to report spam is through the abuse@ email contact of the owner of the IP address which sent the ...
- 248k
21
votes
Is it becoming impossible to be a small mail provider?
There should be no issues becoming a small mail provider. You seem to be doing the right things. Many large providers don't get things right, and hopefully get most of their mail delivered.
If mail ...
- 28k
21
votes
Accepted
How can I reject base64 encoded spam email?
Don't do this with Postfix body_check but write a Spamassassin rule for it, instead. Spamassain decodes the message body before applying its rules. Something like:
body LOCAL_QUANZHOUCOOWAY /...
- 49.8k
18
votes
Postfix, how can I reject spam from unknown IP (no DNS)
You're looking for reject_unknown_client_hostname.
From the documentation:
reject_unknown_client_hostname (with Postfix < 2.3:
reject_unknown_client)
Reject the request when 1) the client ...
- 248k
18
votes
Spam emails regarding Domain Abuse Notices
This is some attempt to spam/phish/infect with malware. Just delete it and carry on.
There is no real way to avoid this crap, but you have your full contact information including mail in the domain ...
- 99.6k
14
votes
Accepted
Detect spammers on my server
Before I get to my suggestion, I want to comment a bit on something your provider said to you:
Received: from mail.com ([94.130.34.42])
by smtp-27.iol.local with SMTP
id ...
- 248k
12
votes
Accepted
Is greylisting still an efficient method for preventing spam?
Update 2019: Conditional Greylisting is the best trade-off
After having used greylisting on all mails for a long time on a busy mailserver, I stopped doing so. It delays ham mails unnecessarily. This ...
- 291
12
votes
How does DKIM work when sending emails from multiple sources/servers?
Explanation
The purpose of DKIM is to sign message headers and body, enabling validation of the origin of the message and that it hasn't been modified. A better reputation on some spam filters is just ...
- 49.8k
11
votes
How can I reject base64 encoded spam email?
Technically, you could directly filter the base64 encoded data for keywords. I'm not saying it's a practical or a reasonable thing to do, given the existence of better and simpler alternatives (as ...
- 905
11
votes
Significance of NOQUEUE: reject: RCPT in Postfix log?
"NOQUEUE" means that Postfix did not queue an incoming message.
"Reject" means that Postfix rejected an incoming message.
"RCPT" means that Postfix rejected the message after the client sent RCPT.
"...
- 248k
10
votes
Are SPF needed for domains that do not send mails and do not have MX record?
If you don't intend to send mail from this domain, why let anyone else to use it as they wish? But things have changed since this question was asked eight years ago. SPF can only protect your domain ...
- 49.8k
10
votes
Is it becoming impossible to be a small mail provider?
One thing missing in the above (excellent) replies is to set up outbound TLS. Gmail has started to punish senders not using TLS, and other providers aren't saying anything but I'm sure they will ...
- 514
9
votes
Spam emails regarding Domain Abuse Notices
If you go to mxtoolbox, and check your domain for blacklisting, it doesn't return as listed on any at this time.
You can check for blacklisting on:
http://mxtoolbox.com/blacklists.aspx
If you check ...
- 2,781
9
votes
Accepted
Is an MX-record required on a domain to send emails only?
No and yes.
By standard, your sender domain is not required to have an MX record. RFC 5321 makes an MX record optional.
However, an MX record is somewhat of a standard today. Due to spamming practices,...
- 11.7k
9
votes
Accepted
Not receiving any RUF DMARC reports (forensic) but are getting RUA (agg reports)
As mentioned in the comments by @anx, hardly any mailbox hosting service ever sends forensic/failure reports anymore. And for good reason. There are several quality DMARC report visualization services ...
- 1,033
8
votes
How to send emails and avoid them being classified as spam?
Detailed solution to avoid emails to be identified as spam and/or not arriving to receivers
Example situation: You have a server running a PHP website for example.com that needs to send emails. And ...
- 739
8
votes
Accepted
Need help determining origin of spam email
Please don't obfuscate your server's identity. It make it impossible to check the DNS configuration to assist you.
You are incorrect in believing that all received are forged. However, they may be. ...
- 28k
8
votes
Accepted
Why would Spamhaus continue to add an IP to the CSS when that IP hasn't sent email recently?
Warning ahead for people experiencing similar issues: NEVER just request unblocking at any spam block list before you figure out what's going on. Those spam blocklist are almost always clever enough ...
- 9,783
8
votes
Postfix: How to accept email with valid SPF but unresolvable hostname?
This could be possible if check_policy_service responded permit (from access(5) other actions) instead of neutral accept action OK vs. reject action reject. That would need modification to the SPF ...
- 49.8k
8
votes
Does DKIM alone not solve the spam issue? Why do I need SPF?
While the answer from Esa Jokinen is right, I find the language confusing.
Put simply:
SPF checks the mail arrived at your server directly from particular agreed authorised mail server(s) or mail ...
- 317
8
votes
Does DKIM alone not solve the spam issue? Why do I need SPF?
I think one of the reasons this is hard to satisfactorily answer, is because your core argument seems to be based on a theoretical ideal situation, not on the real world.
In principle, is DKIM not ...
- 181
8
votes
Why does rspamd consider an odd number of URIs in an email to be an indicator of spam?
Came across your question because I had the same question.
From what I understand in looking through things the logic as follows:
This test is applied specifically to "multipart/alternative" ...
- 81
8
votes
Accepted
Reject emails that fail reverse hostname resolution
Just replace
smtpd_client_restrictions = reject_unknown_reverse_client_hostname
with
smtpd_client_restrictions = reject_unknown_client_hostname
.
From the Postfix manual:
...
- 12.6k
7
votes
Accepted
DMARC: must rua email match domain?
First of all, I don't know if there are any issues specific to how Gmail handles this.
Generally, however, while the DMARC spec does allow for reports to be sent to an external address, it also has ...
- 35.5k
7
votes
Accepted
Fixing DKIM_SIGNED score from -0.1 to positive
I think, this is ok, as is decribed in test details
This negative score will become positive if the signature is validated. See immediately below.
and below are two lines with positive score, so ...
- 1,368
7
votes
Detect spammers on my server
In this day and age, trying to do your own mail server is, for the most part, a loosing battle and you are better off finding an affordable service. Having said that..
Look at your logs going to the ...
- 280
7
votes
Accepted
Does DKIM alone not solve the spam issue? Why do I need SPF?
With DKIM only, there is no way for a receiving server to know where to find the DKIM key for your domain because the signature of the email is what includes the selector DNS record location, which is ...
- 3,137
Only top scored, non community-wiki answers of a minimum length are eligible