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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.

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How to change the sender address using mailutils and postfix?

May 27 14:19:33 localhost postfix/qmgr[21793]: 87FD870AD12: from=user@localhost, size=398, nrcpt=2 (queue active) May 27 14:20:03 localhost postfix/smtp[22591]: connect to mail.rungel.net[95.168.160....
OnionTest5's user avatar
-2 votes
0 answers
30 views

SES SMTP credentials are leaked multiple times [closed]

We are using SES SMTP with cPanel webmail (Exim) and PHP to send emails. This issue happened today and last week. Currently, We have the credentials in 2 places: 1- Exim configuration. 2- PHP files. ...
Dev's user avatar
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0 votes
2 answers
212 views

554 5.7.1 Relay access denied - cant send mails

I tried to upgrade debian from 10 to 11 and the everything got messed up. Im trying to fix postfix. I can receive emails but cant send. I get the error "554 5.7.1 Relay access denied" My ...
Anarkie's user avatar
  • 11
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0 answers
24 views

How to add your own private keys to postfix configuration for DKIM without opendkim or the likes of it?

I have generated the keys locally through openssl added key.pub to the DKIM DNS txt Record but how to add it to postfix withouth any other tool.Is there any connfiguration parameter where the file ...
Abu Shahrin's user avatar
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0 answers
25 views

Cant restrict SMTP connection by IP in Amazon SES

I use Amazon SES to send transactional emails (using SMTP connection) from my app and I wanna improve the credentials security by restricting access from specific IPs. I've created an IAM Policy for ...
Arivan Bastos's user avatar
0 votes
2 answers
124 views

Even though I got full score in mail-tester, gmail still gives an error of IP address not being authorized when using sendmail

I'm using sendmail and I passed the DMARC, SPF and DKIM but when I send an email to [email protected], I get this below error: 50-5.7.1 The IP you're using to send mail is not 550-5.7.1 authorized to ...
John Sall's user avatar
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1 answer
85 views

SMTP Server: Postfix w/ Dovecot - how to configure the allowed username + password?

I seek a Linux-based SMTP server. I've read tutorials and specs regarding Postfix SASL with Dovecot, though I can't find how to configure the list of username and password which are allowed to send ...
Dor's user avatar
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1 vote
0 answers
87 views

How can I make MIAB automatically copy all mail sent via SMTP into the sent folder of the sender's account?

I run Mail-In-A-Box on my mail server and one of my clients is using a specialized application to send messages via SMTP from their account on my server. When they used their own Gmail account to send ...
Del tree's user avatar
0 votes
0 answers
78 views

All containers on a server fail to send SMTP requests, the rest works fine

We have a VPS with several services in Docker containers, on top of which, another Docker container runs a Traefik reverse proxy. Last Monday morning, all the services running on that server failed to ...
Arpenn Sardin's user avatar
0 votes
3 answers
241 views

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, ...
jamminjames's user avatar
1 vote
1 answer
97 views

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 ...
symcbean's user avatar
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1 vote
0 answers
31 views

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: ...
triatic's user avatar
  • 35
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0 answers
27 views

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 ...
mirolz's user avatar
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58 views

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 ...
Paul Lemmons's user avatar
0 votes
1 answer
196 views

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....
EAK TEAM's user avatar
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1 answer
208 views

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 ...
InterLinked's user avatar
0 votes
0 answers
111 views

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@...
mwarble's user avatar
  • 11
0 votes
1 answer
46 views

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-...
test1's user avatar
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0 votes
1 answer
95 views

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 ...
digijay's user avatar
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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 ...
glenatron's user avatar
  • 235
-1 votes
1 answer
62 views

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 ...
imvain2's user avatar
  • 121
7 votes
2 answers
936 views

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 ...
Paul's user avatar
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-1 votes
3 answers
167 views

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 ...
StevieD's user avatar
  • 562
0 votes
2 answers
158 views

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 ...
Kwaku Appiah's user avatar
-1 votes
1 answer
89 views

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 ...
Ronnie Overby's user avatar
0 votes
1 answer
206 views

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 ...
Ryan Griggs's user avatar
  • 1,023
0 votes
1 answer
259 views

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 ...
Denis's user avatar
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0 answers
133 views

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 ...
ZeRedDiamond's user avatar
0 votes
1 answer
151 views

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 ...
Amauri Gabriel's user avatar
0 votes
0 answers
137 views

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 ...
Shinomoto Asakura's user avatar
0 votes
1 answer
132 views

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....
beowulf_222's user avatar
0 votes
2 answers
92 views

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 ...
Thor-x86_128's user avatar
0 votes
1 answer
149 views

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[...
Deckard's user avatar
  • 198
0 votes
3 answers
254 views

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 ...
sashkent3's user avatar
0 votes
1 answer
276 views

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 ...
Stephen Jacob's user avatar
0 votes
0 answers
164 views

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 ...
hitan_999's user avatar
0 votes
1 answer
635 views

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: ...
TomGrill Games's user avatar
0 votes
0 answers
271 views

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 ...
Dio Anderson's user avatar
0 votes
0 answers
158 views

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 ...
imvain2's user avatar
  • 121
0 votes
2 answers
903 views

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 ...
Merc's user avatar
  • 807
0 votes
1 answer
193 views

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 ...
StinGer's user avatar
0 votes
0 answers
234 views

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 ...
espeed's user avatar
  • 159
0 votes
2 answers
436 views

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 ...
Digital Joe George's user avatar
1 vote
1 answer
232 views

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 ...
Pa0x43's user avatar
  • 15
1 vote
1 answer
131 views

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 ...
DHoll's user avatar
  • 11
0 votes
3 answers
133 views

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 ...
David White's user avatar
0 votes
2 answers
2k views

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 ...
supmethods's user avatar
0 votes
0 answers
353 views

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 ...
Starnuto di topo's user avatar
0 votes
0 answers
21 views

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 ...
munishhh's user avatar
0 votes
0 answers
94 views

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 ...
Andy5's user avatar
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