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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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Exim Smarthost setup works in starttls but not in smtps

I have setup my exim4 as a local mta with smarthost delivery (debian 10 vm) following this guide: Exim on DebianWiki If my smarthost is expecting a ssl connection (smtp over ssl) it does not work. ...
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For smtp relay, what is required for postfix to authenticate to gmail's smtp server?

I build websites within a private home-office network. Locally hosted website are development versions of sites that I build for clients. I want the websites that I am building to be able to send ...
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1 answer
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SMTP not available for installation in Windows Server vnext [closed]

I am trying to setup a SMTP service server in my virtual machine, a Windows Server preview, build number of 10.0.2511x. I am not able to find the service for download even in the "Add roles and ...
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1 answer
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Ubuntu 18.04 - SMTP ERROR: Failed to connect to server: Connection refused (111)

I have this new error since 2 weeks on my server. I haven't touched the code or anything. I usually send mail trough PHPMailer, but I noticed Thunderbird won't work anymore also. I'm on Ubuntu 18.04 ...
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-1 votes
2 answers
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How to send an email with openssl and Microsoft Exchange Online?

With Microsoft disabling basic auth in Exchange Online, I set out to add support Modern Authentication in our application. Our app sends basic email alerts. Currently we use SMTP basic auth or open ...
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Force non-empty MAIL FROM for outgoing email

I am using postfix on a Debian server, primarily to send outgoing email for websites and notifications, and have run into an issue where outgoing email to a certain mailing list provider is rejected ...
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-2 votes
1 answer
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How to fix spam listing of IP due to SMTP HELO banner

Spamhaus has listed my IP a few times for an apparent problem. They are indicating: A device using <ipv6 addr> is infected with malware and is emitting spam. <ipv6 addr> is making SMTP ...
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Sender dependent relay with transport maps in postfix

We have some SMTP server in our company. We have transport maps in which we define what domains send to other smtp server. Now, we need sender dependent config for some users. The users are using same ...
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1 vote
1 answer
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Setup postfix exclusively for local delivery

For development purposes I wanted an smtp server, that simply places all mails into a local mailbox. To achieve this, I tried to setup a minimal postfix system. # master.cf smtp inet n - n ...
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1 answer
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Postfix bar authentication from internet

I have a Postfix e-mail server which should allow internal users to send and receive mail via it. The sending should happen only when a user succeeds in a VPN connection which provides him/her with ...
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1 answer
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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 address@mydomain.com, to a gmail account, it gets stuck in the gmail ...
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  • 115
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1 answer
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How do I configure postfix to reject all email that doesn't have a specific 'from' field?

I have an SMTP relay that relays to our email forwarding server but currently it's accepting mail from all sorts of nasty spammers and our email forwarding host have (rightly) suspended the forwarding ...
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Configure host base Postfix and send emails using a container

I have installed and configured the nano /etc/postfix/main.cf file for postfix in the host server and when I try to send it from the host server echo "Test Postfix Gmail SMTP Relay" | mail -...
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Setup postfix as smtp relay

I have a running centos 7 server with postfix configured to allow incoming mails to my domain, say, to test@example.org Now I want to send a mail FROM this test@example.org. My old ISP used to have a ...
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1 vote
1 answer
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How can I use E-Mailrelay to implement DKIM?

I am trying to add DKIM to an existing windows server which is currently using IIS SMTP for outgoing mail. It seems like this could be done by using E-Mailrelay. Unfortunately I could not find any ...
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Mailcow - emails stuck in sending queue for localhost domain

I have mailcow installed using docker and runs very well in sending and receiving mails using the defined domain. I have no customization implemented or configured. BUT.. I have the following issue: ...
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  • 101
1 vote
1 answer
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How to replace "via amazonses.com" with my apps branding "via example.com" for the email identities in AWS SES?

So in SES - there are two ways to verify identities as I can see: Email identities Domain identities With domain identiies - it is easier to fix the "signed-by" and "mailed-by" ...
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  • 125
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1 answer
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Postfix Recipient address rejected: Access denied error after removing permit_mynetworks

I have a mail server which have to remove "permit_mynetworks" from Postfix configuration file(main.cf) in case of abuse. I only set it to allow SASL autheniented relay. But now, postfix ...
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Personal OpenSMTPd relay fails when using "tls-require", works fine with just "tls"

I'm currently setting up a somewhat unique personal email server using OpenSMTPd. I have a local server (Raspberry Pi) and a remote server (VPS). Emails sent to me are sent to the remote server and ...
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gmail smtp vs sendmail configuration in windows and centos

I've got a local server (Windows 10) with XAMPP on it, and for testing Centos 7 with cPanel/SSH access where a Laravel application is hosted. In both cases mail host is set as 'smtp.gmail.com'. When I'...
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1 vote
1 answer
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How do I tell Dovecot to use another server for SMTP?

I am a bit lost on mail servers, but I have to install a mail proxy (Proxmox Mail Gateway) in front of the actual mail server (ISPConfig, Roundcube, Dovecot, Postfix). On receiving emails, it uses the ...
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1 answer
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Can't get incoming mail over TLS for Postfix SMTP Relay

I have a Postfix Ubuntu VM acting as a mail relay server, which accepts mail on port 25 and forwards it on to Microsoft Exchange online for delivery. This has been working fine for months. Now I need ...
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0 votes
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Postix to relay SMTP from port 587

I have a debian server with postfix, fail2ban, roundcube, webmin and dovecot installed on it. I have been able to send mails from port 25, but regardless of what I try I can't get it to work from 465 ...
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1 answer
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Outlook / MS Exchange from Office 365 returns 550 header syntax

A client of mine has a case that a partner company is not able to deliver e-mails to them. The case is that they receives following information returned by Mailer-Daemon: This message was created ...
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  • 101
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Forwarding emails from hMailserver through postfix to their destination

Right now my email config is the normal sender -> server -> server -> receiver, but since the first server (sender side) is behind a residential IP, it is on a blocklist and isn't accepted in ...
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SASL PLAIN authentication failed: bad protocol / cancel

I try to configure postfix relay in kubernetes on Alpine using saslauthd. Dockerfile: FROM alpine:3.15 RUN apk update && \ apk add --no-cache postfix \ libsasl \ cyrus-sasl \ ...
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How do I resolve the "Snapin Error" when setting up SMTP on IIS Server?

I have installed IIS 6.0 Manager and SMTP Server. When I right-click on [SMTP Virtual Server #1] and then click on Properties, I am getting this error "MMC has detected an error in a snap-in. It ...
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0 votes
1 answer
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ufw configuration for smtp connections

I have a PHP application running on a Debian server with UFW as firewall. The application needs to connect to a SMTP to send mails. It works when I disable UFW. When it's enabled, the PHP application ...
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1 vote
0 answers
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Can't configure SMTP encryption - postfix

I have docker-mailserver and Roundcube in containers, beside there is MySQL database for mail data and user passwords. Dovecot inside is configured to verify logging in users passwords with database. ...
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  • 159
1 vote
1 answer
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Postfix still uses port 25 despite configuration saying port 587

I have a postfix server that is a relay for the main mail server. That main mail server is to be used with the 587 port when i do a telnet on it it works just fine : telnet 10.10.10.10 587 Trying ...
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Azure outbound communication SMTP

I'm trying to configure SMTP on an Azure Windows server. There is a public IP address and a Network Security group. On my local machine I can test an SMTP server and it works, for example telnet> ...
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0 votes
0 answers
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Error setting up SMTP via Exim4

I just started at my current role and I'm the only IT guy... I have a server that is used to send emails to a local smarthost but they just switched to using Office 365 and it "never worked" ...
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0 votes
1 answer
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Is rejecting email based on IP address in chain allowed?

A major ISP is rejecting email (bouncing with error 550) on the basis that an IP address in the transmission chain is on their 'blocklist'. Are they allowed to do this and still be IETF compliant? ...
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  • 101
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2 answers
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Enable SMTP Port 587 instead of Port 25

Through my Office365 subscription, I have an SMTP relay, ‘contoso-com.mail.outlook.com’. Currently this only accepts traffic on port 25 I want to look at setting up port 587 with TLS encryption, but ...
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1 vote
1 answer
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Using TLS1.0 or TLS1.1 to connect to Exchange Online with SMTP AUTH

I have a Windows Server 2008 R2 that is being replaced in two months. Currently we use it for sending out reports, invoices etc. with SMTP Relay from multiple applications that are also being replaced ...
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0 answers
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Is it possible to trigger a 550 SMTP answer from a script Postfix piped a mail to?

I want to prevent backscatter from within a mailing list script that I use on my Postfix mail server. Mail for a mailing list hosted there is piped to my script. At this point, Postfix can't know if ...
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0 votes
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Postfix won't connect to relay SMTP server

We have a Debian virtual machine and I want to use postfix and mailutils to send email via a relay SMTP server Trying to connect to the SMTP server with telnet works. telnet mail.sch.gr 587 Trying 194....
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How to hide origin IP of SMTP server by tunneling/proxying incoming port 25 traffic to real mail server

We have most of our stuff behind Cloudflare. However, some services such as mail (ex: mail.mydomain.com MX record) cannot be pushed through cloudflare and they expose our mail server's IP which makes ...
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0 votes
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Postfix spoofed messages using an alias which forwards emails back to the sending domain

My Postfix installation has the following alias configured which will distribute incoming emails to the following addressees : alias@my_domain.com - goes to - me@my_domain.com alias@my_domain.com - ...
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SPF records with a dynamic IP to a smtp relay with Office 365

I'm helping out a client setup an smtp relay because our software is failing at times to send email when using the smtp server of smtp.office365.com and we have found that setting up a smtp relay via ...
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0 votes
1 answer
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SMTP relay with FQDN, but SpamAssassin marks FSL_HELO_NON_FQDN_1 and HELO_NO_DOMAIN

my mail provider (posteo.de) offers an FQDN during the HELO/EHLO exchange (e.g. mout2.posteo.de) – which is seen by policyd-spf (s. below) – but SpamAssassin on a receiving server marks the relay as ...
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STMP connection error with roundcube

recently I was trying to install roundcube on my server and everything works fine until smtp test. When I try to connect i always get this error: SMTP send: NOT OK(Connection failed: Failed to ...
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0 votes
1 answer
108 views

Why does Outlook only connect to my server but not send any email?

I don't have any problems receiving email from Gmail, or any of the mailing lists that I've signed up for, but for some reason Outlook refuses to send any email to my mailserver. _handle_client ...
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Zimbra Setup, can receive emails, but I cannot send emails

i installed zimbra on my Cloudserver (Digital ocean) i can receive emails from other external emails but sending is an issue, I have also set up DKIM, SPF, DMARC for the emails but i still cannot send ...
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0 votes
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SSMTP: Map local user (UID greater than 1000) to an external email address

I've configured SSMTP to send system messages for users with a UID < 1000 in /etc/ssmtp/ssmtp.conf: root=to@mydomain.com rewriteDomain=mydomain.com If I send an email to root (echo test | sendmail ...
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  • 4,937
2 votes
2 answers
160 views

DKIM: Can I safely add a DomainKey policy record without breaking existing email?

I need to setup DKIM to validate an email provider we are using. In the provider's documentation, they require us to add two records, a selector record and a policy record, like this: selector....
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0 votes
2 answers
68 views

WebApp needs to send emails via Outlook.com mail account

I have a web app running on a shared server account for the domain example.com. The web app needs to send the occasional email to the app adminstrator. The domain example.com is using Outlook.com as ...
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0 votes
1 answer
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postfix: how to force IPv4 through SMTP?

Problem I have successfully set up a Postfix mailserver with an SMTP interface, set up DKIM, DMARC, SPF, all that stuff. But I had a problem when testing the delivery of emails to Gmail. Namely, SPF ...
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1 answer
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Postfix / mailutils Mail appears to be sent in logs, but not in the mailbox

I've seen few of this question here but I couldn't find a solution for it. I'm currently trying to set up Postfix with mailtutils, but I can't see my incoming emails in my mailbox, so I am not sure if ...
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1 vote
1 answer
36 views

Require authentication from subset of mynetworks in postfix

Is it possible to configure smtp for postfix to require authentication, (e.g. with smtp_sasl_auth_enable = yes), for certain IP ranges but have other ranges un-authenticated? For our local network we ...
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