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Issue spf: stderr: SKIP

J

JamesWhitaker

New Pleskian
Server operating system version
Ubuntu 24.04.4 LTS
Plesk version and microupdate number
18.0.81 #3
Hello,

I'm having some problems with my email configuration.
SPF spam protection is enabled in the settings and set to: "Only create Recieved-SPF headers, never block".
However, such a SPF_header is not added to the emails I recieve.
Some emails mention SPF in the "Authentication-Results", most do not:

Authentication-Results: sub.sender.com;
dkim=none;
dmarc=pass (policy=quarantine) header.from=sender.com;
spf=pass (sub.sender.com: domain of [email protected] designates 000.111.222.333 as permitted sender) smtp.mailfrom=[email protected]

DKIM is also enabled and works perfectly fine.
In the logs I see a lot of mentions of:

spf: stderr: SKIP
check-quota: stderr: SKIP

I think the Plesk mail filter skips the SPF check for some reason.
Any suggestions as to why are much appreciated!


OS: Ubuntu 24.04.4 LTS
Product: Plesk Obsidian 18.0.81 Update #3
 
spf: stderr: SKIP and check-quota: stderr: SKIP usually indicate that the messages are from authenticated senders, thus, the SPF checks were skipped. About the Authentication-Results header, could you please provide an example of the full message header?
 
Hello, thank you for your response!
To clarify, what exactly do you mean by "authenticated senders"?
The emails in question are from external servers like outlook, or some company's server.

I have not had any problems with emails sent between users on the plesk server.
For example, these are the headers for an email sent from user A to B (both on the plesk server):


--------------------------------------------
Return-Path: <[email protected]>
X-Spam-Checker-Version: SpamAssassin 4.0.0 (2022-12-13) on
myserver.stratoserver.net
X-Spam-Level:
X-Spam-Status: No, score=-0.2 required=7.0 tests=DKIM_SIGNED,DKIM_VALID,
DKIM_VALID_AU,DKIM_VALID_EF,NO_RELAYS,SPF_PASS autolearn=ham
autolearn_force=no version=4.0.0
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: by myserver.stratoserver.net (Postfix) with ESMTPSA
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=domain1.com;
s=dkimselectordomain1; t=1792081044;
bh=WwalFtLwee7PSxQMtQQM77/TjrmWZNbGSdyHmGHr5Ho=; h=To:From:Subject;
b=BWVk+lEktRZr0lCFpz0UDb4+H0fWRJfyuB4HNq53L6wvQ/dhdghcHOJ+4IDdiyLIa
004K6XCzfywOtk9jRMxBo8PCgWNzzGe87x2VNd7AAcLrs7smMjRY9cacwEb4p7iouG
2ilpH+abfA+MWonjMmzS5BHa3mEX1eAs1Ane8h3HHTJmTUyVZ+/U0Q8OKVTADfb0LA
nSUmNbqnkW8yUQC7exvMotijM8RK8ku80H9uyvTuqJ1s75vvKWHrujCcOWZbN9XYOb
lSDNqWKl2H8vg==
Authentication-Results: myserver.stratoserver.net;
dkim=pass header.d=domain1.com;
spf=pass (sender IP is <my-private-home-ip>) smtp.mailfrom=[email protected] smtp.helo=[<my-internal-device-ip>]
Received-SPF: pass (myserver.stratoserver.net: connection is authenticated)
Date: Thu, 15 Oct 2026 18:17:24 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Content-Language: en-US
To: [email protected]
From: User1 <[email protected]>

------------------------------------------------



However, email from 3rd parties does not have the "Received-SPF" header.
Sometimes SPF is mentioned in the "authentication-results" (or "arc-authentication-results"), sometimes it is not:



------------------------------------------------

Return-Path: <[email protected]>
X-Spam-Checker-Version: SpamAssassin 4.0.0 (2022-12-13) on
myserver.stratoserver.net
X-Spam-Level:
X-Spam-Status: No, score=0.0 required=7.0 tests=HTML_MESSAGE autolearn=ham
autolearn_force=no version=4.0.0
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: from sub.organization.com (sub.organization.com [00.11.22.33])
by myserver.stratoserver.net (Postfix) with ESMTPS id 1FD38BB6165B
for <[email protected]>; Sun, 11 Oct 2026 16:07:18 +0200 (CEST)
Received: from localhost.sub.organization.com (sub.organization.com [00.11.22.33])
by sub.organization.com (Postcow) with ESMTP id AE30486F335
for <[email protected]>; Sun, 11 Oct 2026 16:07:10 +0200 (CEST)
Received: by localhost.sub.organization.com (Postfix, from userid 33)
id 1FE9286F253; Sun, 11 Oct 2026 16:06:51 +0200 (CEST)
To: [email protected]
Subject: Newsletter
Date: Sun, 11 Oct 2026 16:06:51 +0200
From: Organization <[email protected]>
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="b1=_3ULwDVMSRCZenrtzamGV77jizSZ0X1tyncnpz89qcQ"
Content-Transfer-Encoding: 8bit
X-Last-TLS-Session-Version: None
X-Rspamd-Queue-Id: AE30486F335
Authentication-Results: sub.organization.com;
dkim=none;
dmarc=pass (policy=quarantine) header.from=organization.com;
spf=pass (sub.organization.com: domain of [email protected] designates 00.11.22.33 as permitted sender) smtp.mailfrom=[email protected]
X-Spamd-Result: default: False [-5.88 / 15.00];
NEURAL_HAM_LONG(-4.00)[-1.000];
NEURAL_HAM_SHORT(-2.00)[-1.000];
IP_REPUTATION_HAM(-1.27)[asn: 1103(-0.36), country: NL(-0.01), ip: 00.11.22.33(-0.90)];
URI_COUNT_ODD(1.00)[5];
AUTOGEN_PHP_SPAMMY(1.00)[];
DMARC_POLICY_ALLOW(-0.50)[organization.com,quarantine];
R_SPF_ALLOW(-0.20)[+a:sub.organization.com:c];
RCVD_NO_TLS_LAST(0.10)[];
MANY_INVISIBLE_PARTS(0.10)[2];
MIME_GOOD(-0.10)[multipart/alternative,text/plain];
MX_GOOD(-0.01)[];
HAS_PHPMAILER_SIG(0.00)[];
RCPT_COUNT_ONE(0.00)[1];
WHITELISTED_FWD_HOST(0.00)[131.174.31.37];
RBL_NIXSPAM_FAIL(0.00)[131.174.31.37:query timed out];
MAILCOW_DOMAIN_HEADER_FROM(0.00)[organization.com];
TO_MATCH_ENVRCPT_ALL(0.00)[];
ARC_NA(0.00)[];
BCC(0.00)[];
R_DKIM_NA(0.00)[];
FROM_EQ_ENVFROM(0.00)[];
TO_DN_NONE(0.00)[];
FROM_HAS_DN(0.00)[];
MIME_TRACE(0.00)[0:+,1:+,2:~];
MID_RHS_MATCH_FROM(0.00)[];
ASN(0.00)[asn:1103, ipnet:131.174.0.0/16, country:NL];
RCVD_COUNT_TWO(0.00)[2];
WL_FWD_HOST(0.00)[]


---------------------------------------------

ARC-Seal: i=1; cv=none; a=rsa-sha256; d=mydomain.com; s=scdk886;
t=1791727391;
b=mQwbDznA1TtY+MmbX/WFggqOiHbj+7ZNIT2tvz56GVTOdUdEpSxIzaW82zc0sFY+14tk9
zv0NvNawk3NcUiLET88Hojlo19oHmMm76CNeOamiIFJ0L2Q/QPzzh7LAEAHWfZIbZNrNzoH
fTGYSlw5c4foXPqjHBx5Q+ylGtZQGuR4gHYHr2vx0cRzVXGy0CeIrDRBClV9sNvwkTD6uBT
wmgHqPHrMO+uvs3huE1oLHbV/n+l/W/mZP3bxyaN0xN5Infsk9E4Vl4gMwU8ZvCY7vKe+rS
1QDFppDNGYGCr2Hho+GsnW1Nk+C0Go3Kn11jH7byG533zwmJx/wy5NKATPUw==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed;
d=mydomain.com; s=scdk886; t=1791727391;
h=content-transfer-encoding : content-type : date : from :
mime-version : message-id : subject : to : from;
bh=fbgAbwyGBIfjX36d14qYDO52T3OSvnFmc2j2T1PQoQc=;
b=a2SEKwF6wR8ysirB0RcJTFqSnFwjZENdg4r5I0DbTmpXTchNrng3p/YkiEiplA3NClUpG
ybVFAbQYRYeuXinw7Bxl8kicpeExN0vfxINe9GrfC6ugncaoh/1dQhxRQCguvzBnITWcyWD
U4cuKG7rV4VPTcJNQ72kq9qCooPRff2Dn5yl33bFX5TI3HLY13E0rLxUrge4sVEuolFC4uC
wa3qzN0VU1oJMSJvJyzqUD/NgKumHH4M9xeMwNXyzW9xp9WripX5FQe67enj6VvJPNAGIvl
vjuMN0SqZElpnDm69ksVdSusRDWM7cT5lLn3b2xbL0RaaQwvKX8P4F76EbXw==
ARC-Authentication-Results: i=1; myserver.stratoserver.net;
dkim=pass header.d=company.com
X-Spam-Checker-Version: SpamAssassin 4.0.0 (2022-12-13) on
myserver.stratoserver.net
X-Spam-Level:
X-Spam-Status: No, score=0.0 required=7.0 tests=DKIM_SIGNED,DKIM_VALID,
DKIM_VALID_AU,HTML_FONT_LOW_CONTRAST,HTML_MESSAGE,MIME_HTML_ONLY,
T_REMOTE_IMAGE autolearn=ham autolearn_force=no version=4.0.0
Authentication-Results: myserver.stratoserver.net;
dkim=pass header.d=company.com
Return-Path: <[email protected]>
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: from s.wrqvtzvf.outbound-mail.sendgrid.net (s.wabcdef.outbound-mail.sendgrid.net [149.72.126.143])
by myserver.stratoserver.net (Postfix) with ESMTPS id 4BF5BBB6165B
for <[email protected]>; Sun, 11 Oct 2026 16:03:10 +0200 (CEST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=company.com;
h=content-transfer-encoding:content-type:date:from:mime-version:subject:
to:cc:content-type:date:from:subject:to;
s=sg; t=1791727388;
bh=fbgAbwyGBIfjX36d14qYDO52T3OSvnFmc2j2T1PQoQc=;
b=ScaFx3NV59RRJNk5yWi37a7nyUPSKImTDQXdCVPx+BmeOQa2BV176Zh8IQV4FJCzCmu8
WJ3G84Uk3aeIWj1z5g9bZV1xcIqP9MJvyHiNirtWvkLCZHzvh1L5wwBuqlkdqCAYnp6P2/
KjbqVyqx4JRHfd01egpWmw+aUVI+JDOW0Eg3ZTfiulZEGUmxTXsOmlqh0qAvPletiE8Rv7
ijaLE2/3DC7p+gMFaaSvB4+P90UVGgOaEsjQAudZJg8gHtCTJQD28HXp+aGSSZLzui+Zbl
d+Qmhd2naK941N8EeEtwBHyjpMx4HsFdBRcRNV83Lzy7GGIkyn4lxQhhScXJhBcw==
Received: by recvd-b4fff8755-dpgzd with SMTP id recvd-b4fff8755-dpgzd-1-6ACB9716-76
2026-10-11 14:03:02.478479104 +0000 UTC m=+1026142.492084564
Received: from ODgyNDk3Ng (unknown)
by geopod-ismtpd-13 (SG) with HTTP
id XxHOkcL0RqKB4ynUK6ZThg
Sun, 11 Oct 2026 14:03:02.232 +0000 (UTC)
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html; charset=utf-8
Date: Sun, 11 Oct 2026 14:03:08 +0000 (UTC)
From: "Company" <[email protected]>
Mime-Version: 1.0
 
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