Questions tagged [smtp]
SMTP is the Simple Mail Transfer Protocol, the most recent standard of which is defined in RFC 5321. It's the Internet standard for sending and receiving email.
3,169
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Postfix sending duplicate emails under different userid's, how to fix?
I can't find a reason for it in the postfix settings, but duplicate emails are being sent, under different uid's. Looking at the email headers, they have unique ids, and each with a different Postfix, ...
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Postfix - can't limit active queue
One of the destinations I send email to has unusual performance characteristics. The active queue can fill up with messages for this domain, blocking sending to other domains. I want to limit the ...
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Cannot get Exim to verify DANE for remote smtp
I am trying to configure Exim to try DANE before deciding to deliver unencrypted mail to remote hosts.
My general Exim configuration has: dns_dnssec_ok = 1.
For the dnslookup router: ...
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authenticate users in smtp relay server exim4
I'm configuring relay SMTP server for sending email alerts from my local network. I need to send emails alerts from services witch run on my servers. And I need to authenticate it: each service should ...
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Security concerns with self-signed Xerox device certificates during SMTP transfer
I am trying to find out what risks there are in a SMTP connection which uses a self-signed certificate for TLS.
The setup is a Xerox MFP which is being used to send emails for scan to email ...
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44
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postfix MTA seemingly benign I/O Error : postqueue fatal: output write error: Input/output error
I am getting the following message in my syslog exactly every 30 seconds. Everything is working but words like "Fatal" and "Input/output error" cause me an inordinate amount of ...
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VM behind nat on Proxmox cannot reach port from internal network
The issue is that I am able to reach port 25 from outside (public internet) to the specific machine in the local network behind NAT, but cannot reach to port 25 on public machine e.g. hotmail-com.olc....
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157
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How to install sendmail client only, without the MTA?
Is there any way to install the sendmail client, only, without installing the sendmail MTA at all?
What I mean by this is the sendmail -t command that is frequently used by processes such as cron to ...
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63
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Email Sender Identities / Single Sender Verification
I have a self-hosted web service and one of its features is allowing customers to send emails to their customers. Currently we send these emails on behalf of our customers by setting:
from: mailer@...
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How to send email from smtp server1 to smtp server2 (Postfix) via client?
How to make server1 with postfix can send email to server2 with postfix by redirecting DNS query to it (type forward). These servers are on the same local network. Server1 is to receive a non-...
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43
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Changing sendmail HELO/ELHO header in docker container
I have a Debian 11 docker container in which sendmail v. 8.15.2 is installed as MTA. Unfortunately spamhaus.org blacklisted the host IP due to the HELO header of mails being sent from this container ...
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Postfix/Dovecot fails to send emails "SASL PLAIN authentication failed" - no further message
I have been all around the houses trying to configure Postfix and Dovecot so I can send through my domain from Gmail, which as far as I know is simply Gmail acting as a regular SMTP client talking to ...
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Telnet SmarterMail: 550 This is a submission only port. You must authenticate before sending mail
I have a "newer" server running Windows Server 2019 and I installed Smartermail FREE Edition so I could send mail via PHP/CDONTs from contact forms to my email address.
I tried matching the ...
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If a lower priority mail server only serves code 450, will sending servers on retry use a higher priority server?
I had a backup mail server eat a bunch of messages and I want to just configure a simple server to send 450 for all messages.
However, I'm not sure this is a good idea because if the sending servers ...
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Outlook getting spurious SMTP errors when connecting to Linux dovecot mail server
I'm running a mail server for about 30 people. I have had zero issues with it. But last week, several users began reporting an error in their email client, Outlook:
Checking the server mail log ...
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How to change the sender / from field using Postfix as SMTP relay server to relay to MSO365 mailbox
My company have set up an Ubuntu 22.04 Server to act as an SMTP relay server to relay messages to our Exchange online mail server.
A user account [email protected] has been setup on the Exchange to be ...
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Why Google SMTP MTA's are not sending STARTTLS command
I'm a software engineer that wrote my own SMTP delivery agent. I recently added the STARTTLS support to my software and I was doing some testing, when I noticed that Google's SMTP transfer agents are ...
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How to use NGINX as legacy SMTP proxy to new SMTP system?
We have some very old radio equipment in the field which uses SMTP to notify us of failures. Unfortunately this equipment does not support modern SMTP authentication methods (SSL, etc), and can only ...
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Original DKIM signing is not sent when using SMTP relay
We are using a VPS (ubuntu 18, postfix) to send mails for multiple domains hosted on a server (AlmaLinux 8). For example from the domain "domain.com".
VPS is maildomain.com
Hosting server ...
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Failed to send SMTP email with PowerShell and Postfix SMTP relay
I tried to correct some errors with a PowerShell script with Send-MailMessage() that sends an email via a Postfix SMTP relay, but it returns this error:
error PowerShell
I found that I should add this ...
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143
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Postfix to not delivery mail to domains using another mail server
I am configuring a hosting + mail setup. I have one server for hosting websites, and one for the smtp/imap/dovecat server.
As far as I researched, the only reasonable way to allow my customers to have ...
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Is possible to use a DKIM-Proxy to signing emails requested from another application?
I using an application to send emails, written in golang which use net/smtp as SMTP Libary, however that lib provide no support with DKIM signing, but using a sendmail command, for example, the DKIM ...
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POSTFIX smtpd relay depending on sender
I am using Postfix on a server mx1.domain1.com to relay e-mails for domain1.com as well as other domains, domain2.net, and domain3.org, which are hosted on the server (domain1.com). In addition, mx1....
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In Postfix, Should SSL FQDN Matches with myhostname or mydomain field in /etc/postfix/main.cf?
Quoted from the documentation:
myhostname
The internet hostname of this mail system. The default is to use the fully-qualified domain name (FQDN) from gethostname(), or to use the non-FQDN result ...
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Warning: you may need to increase the main.cf smtp_destination_concurrency_limit - but it is set?
We have a huge delivery of emails right now and emails are not delivered as fast as I think they would:
In the mail log (Postfix v3.4.13 ) I see the following message
Dec 8 14:34:28 s29 postfix/qmgr[...
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3
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227
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Is opening SMTP port with default Sendmail config safe?
My self-hosted web app (Ubuntu VPS) needs the ability to send noreply@ notifications to users when something goes wrong. I don't really need the ability to receive emails but I would like to comply ...
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Can I generate and log output alerts for SMTP traffic using Suricata 7.0.2?
I have Suricata 7.0.2 IDS installed on a Linux Ubuntu 20.04 virtual machine. In my virtual environment, I have two virtual networks. In the first network, I have a mail user agent (Attacker) that ...
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140
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PAM failing to authenticate all users from one domain in dovecot
I have installed a mail server using Dovecot + Postfix, and it always worked correctly.
Recently I installed a new domain example.com and a user [email protected] for that domain in the mailserver ...
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455
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mailpit / kubernetes: SMTP sendmail cannot connect - telnet works fine
kuberntes setup:
mailpit service + deployment
(ingress works, I can connect to the UI)
---
apiVersion: v1
kind: Service
metadata:
name: desideria-crm-mailpit
namespace: desideria-crm
labels:
...
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197
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Can not setup postfix/dovecot with email clients
Having problems with configure postfix/dovecot with email clients such as outlook and thunderbird.
Using telnet and openssl I have tested both smtp and imap through ports 587 and 993.
Sent mails are ...
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Setting up Windows Server 2019 to allow sending mail in Classic ASP/PHP
I'm working on migrating over to a new server and I'm trying to setup the server to allow PHP/Classic ASP to send emails from forms etc..
I followed these instructions and used the IP 127.0.0.1 where ...
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564
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Email rejected by SMTP server
I am sending automatic emails with a custom written software. The recipient is VERY interested in receiving these emails, since they actively requested then. However, they are complaining they are not ...
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Rewriting message header To: field when sending email
I am configuring an SMTP server with Postfix (v3.7.3) for local (i.e. host only) mail sending on openSUSE 15.5 Leap.
What I would like is to send messages to local "users" (there is no real ...
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stunnel smtp tls frontend server/proxy for remote backend postfix
I'm running stunnel in server mode and listening on port 587 and trying to connect to a remote postfix server running on port 25.
NB: the two servers are connected via zerortier, which may or may not ...
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Can I Force Implicit TLS Connection For Port 587 On Postfix?
I have read many articles saying port 587 by default is explicit TLS. This means it's STARTTLS. It asks the server on an unsecured connection if TLS is supported and if it is, it continues with an ...
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Wrap plain text mail in html
we use Postfix as MTA to send our mails from our system. Unfortunately we have an old persistent system which we cannot change, which sends mails to our customers in plain text format. I would like to ...
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Exchange Online ESMTP responds differently from different clients - Windows 10 vs Windows Server 2019
When I telnet to our Exchange Online's SMTP server address (****.mail.protection.outlook.com, port 25) I get two different responses or types of connect depending on what machine I'm using.
When I ...
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3
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Postfix: How can I handle incoming mail for a single address, not the entire domain?
I've gotten my employer to configure the company-wide Exchange server to forward [email protected] to [email protected], a host I control. So far, so good. My Postfix configuration ...
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Postfix relay to Office 365 - DNS configuration
To reduce the likeliness of email being flagged as SPAM, I believe these are the few things that should be done on email servers:
Hostname resolves to a valid IP e.g. mail.example.com to 1.1.1.1
...
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SMTP, snort: warning 124:3 attempted response buffer overflow
From time to time, I'm receiving a 124:3 warning "attempted response buffer overflow" from SNORT, while sending emails.
What could cause this warning? How can it be investigated? How can it ...
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Postfix 2nd domain
I have two postfix servers(virtual machines) on same host
1st domain = mail.xyz.org
2nd domain = mail.xyz.edu
I want to send mail from 1st domain to 2nd domain.
If i try, it gives error:
Recipient ...
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SharePoint SE not able to send automated emails
I have configured in SharePoint Administration the outgoing emails to an SMTP Server on Port 25.
The SMTP Server is a default setup with anonymous authentication which is the same on SharePoint, and ...
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IIS SMTP Relay to gmail fails occasionally
I'm using IIS SMTP relay to gmail to send outbound emails. I create this email text file with SSIS script task and place the file in the Pickup directory. This script runs every 15 minutes. It works ...
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Why am I getting Sasl errors when trying to authenticate to SES with Postifx?
I am getting these two errors in my mail logs:
Aug 25 22:51:23 ns1 postfix/smtpd[246267]: warning: unknown[94.156.102.101]: SASL LOGIN authentication failed: authentication failure
Aug 25 22:55:22 ns1 ...
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Two mail server installs (for two domains) on Windows VPS with one IP?
I'm starting with 1 IP address and the supplied mail server software license supports only 1 domain.
I'm now adding a second domain to the VPS on the same IP address. There's a LARGE increase in cost ...
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300
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How to configure postfix to reject emails which are pretended to be send from myhostname?
Suppose the Postfix mail service is serving domain @mycompany.com. Local network is 192.168.10.0/24. The attacker from Internet sends an email pretending it originates from @mycompany.com:
Received: ...
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Outlook cannot be configured to receive emails from an SMTP Server [closed]
I have installed an SMTP Server on Windows 2022 to on an internal network. So, outside emails. The server runs, and from another server using both telnet and Powershell I can mimic an email being sent....
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"550 5.1.2 Relay not allowed" Error returned when trying to send emails from my on-premises mail server
I setup an on premises mail server for my domain, to send and receive emails.
I've picked Stalwart mail server for this.
I deployed and configured the system, to the point which I am able to receive ...
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167
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Exim4: (gnutls_handshake): timed out
I'm using Exim4 on the Debian server.
Debian:
Distributor ID: Debian
Description: Debian GNU/Linux 11 (bullseye)
Release: 11
Codename: bullseye
Debian kernel:
uname -a
Linux mail....
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449
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Postfix smtpd_sender_restrictions with logical AND
I am using postfix, I need to configure sender based restrictions so nobody that is not authenticated & not part of mynetworks can send mail through this server,
this is my smptd sender ...