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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MS Exchange: How to enable SMTP to use OAUTH2.0 but with basic AUTH disabled

(I have asked this question also on stackoverflow but I now think that this might be a more useful community to ask hence I am also posting here.) I am trying to know whether it is possible to enable ...
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Use HAProxy as a Forward Proxy for PowerMTA

PowerMTA can use HAProxy as forward proxy to deliver mail using the IP address HAProxy is serving on. This is not the typical use case of HAProxy because it's not load balancing, it is connecting ...
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Cannot send emails from tomcat application

I'm having some trouble with our servers, we run in a ubuntu 18.04 as VM from Vmware ESXI 6.5 with a pfSense firewall as another vm, we have multiple tomcat instances running with no problem. In the ...
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Redhat PostFix implementation - Temporary lookup failure

Trying to set up PostFix as a simple relay server for apps and devices that need to send emails. If in main.cf I set relayhost = [1.2.3.4] where 1.2.3.4 would be IP of my email spam filter (...
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Configure Postfix external relay for UCEPROTECTL3 rejection

Is it possible to configure MTA Postfix server to bypass UCEPROTECTL3 rejection ? Example when my server connect to recipient server then I get information: Diagnostic-Code: smtp; 554 5.7.1 You are ...
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In an Exch 2016/EXO hybrid deployment, should a telnet message test on prem be considered internal

I have inherited a hybrid deployment between Exchange 2016 on prem and Exchange online. One of the first things I had to do was turn of centralized message transport, as it was adding two unnecessary ...
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How can I redirect a external mail server if my mail not found on Postfix?

I have 2 mail servers Gmail server --> Principal Postfix server --> Secondary My configuration is based on host and dns for google, that's ok, but my problem is with postfix. ex: In gmail have a ...
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Postfix catchall if valid email

How is it possible to deliver all emails to addresses which are valid (validated against LDAP) to the same local user? It should check if in LDAP exists a real user with this mailaddress. If so it ...
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2answers
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Best way to serve mails from public SMTP server to the internal mail server without initiate connection from DMZ?

I have a basic question for a mail setup which i have to implement. We have an SMTP server (Postfix) in DMZ, which should receive and accept all mails for our internal users. Then we have a internal ...
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Postfix without queues?

I would like to use Postfix as an MTA to deliver emails that I create locally using a Python SMTP client. But I would like to handle the re-sending of emails manually, rather than using Postfix's ...
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1answer
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Setting up an MX record for a send-only server

I have set up a send-only server and I have tested it using mail-tester.com. I get a 7/10, and I experience a majority of outlook/msn/hotmail inboxes sending my email to the junk folder. I do know ...
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How to do load balance [duplicate]

I have a Linux (CentOS 7) server with 10 IPs. I Would like to use all IPs to sent a mail. For example: "First Outgoing traffic wants to send first IP second Outgoing traffic wants to send second ...
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How to configure NGINX as proxy for local SMTP server?

I am doing some testing with the NodeJS smtp-server module. It exposes a listening SMTP server on any specified port. SMTP usually runs on port 25, but in order to run the Node app as a non-root user,...
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Email not Reaching iCloud Mail Servers

I recently created a new VPS and installed an email server using Modoboa. Everything seemed to be working and fine until I sent an email to an @icloud.com address. The iCloud user never got my email, ...
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Mail bounces: SMTPUTF8 is required, but was not offered

My mail server periodically sends out a newsletter to my clients. This is handled by a Perl script on the server. A few of the recipients names contain non-ASCII characters like ä, é, ö, etc. On my ...
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postfix verify command not running and seems to be delaying mail by 3 seconds?

I've been noticing that my postfix SMTP transactions seem to pause for 3 seconds in the middle. In looking at my SMTP trace logs I see the following: 2021-03-17 00:19:54,869 TRACE SmtpClientImpl - ...
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1answer
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Cannot use my postfix smtp to send mails from gmail

I have a postfix/dovecot setup on ubuntu 20.04, on a remote VPS, allowing only ssl/tls transactions. I can send/receive mails with it from a thunderbird client on my local machine. I can receive its ...
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How to Use Multiple Relay in postfix?

I have a centos 7 server with 5 IPS like 192.168.0.2/29 to 192.168.0.5/29. i have a two relayhost like "smtp1.example.com" and smtp2.example.com. I have configured like this vim /etc/...
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DPM Setup is unable to update the report server configuration to configure e-mail settings. (ID: 3040)

On my System Center 2019 Data Protection Manager Server (with Update Rollup 2 installed) I try to enable e-mail notifications. Whenever I click on OK after entering all details in the SMTP Server tab, ...
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1answer
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Postfix client sasl 465 bounced 550 sender rejected (in reply to MAIL FROM command)

I'm tring to send an email through my mail provider but I get rejected, is there something wrong with my config file ? echo "Hello" | mail -s "hi" you@example.com Gives me status:...
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1answer
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How can I forward email based on the send-from address?

So I have a unique situation. I work for an MSP and we host a Unix server in our environment for a customer that sends SMTP to our internal mail server. The problem is on this unix server, there are ...
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Are SMTPS and IMAPS ports really deprecated?

I've read that STARTTLS command was added and intended to deprecate the SSL ports. But even major mail servers like google still use SSL ports and even don't allow us to use classic ports with ...
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How to enable ESMTP in postfix server

I have setup a posfix mailserver and some of the messages (sent from Microsoft exchange online) are rejected with below error. SMTPSEND.BareLinefeedsAreIllegal; message contains bare linefeeds, which ...
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1answer
63 views

Why would Google be throwing away emails from virtual domains to virtual domains? postfix

I'm seeing some odd behavior and am hoping someone has seen this as well. I have a CentOS server running Postfix for virtual domains for my businesses. It was working well for years and then suddenly ...
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1answer
63 views

Postfix. SMTP (Send only) remote authentication

So I have enabled an Ubuntu Server 20 in the cloud with a dedicated public IP, and I want to use it as a SMTP server for MyDomain.com. I have setup DNS and PTR, so this server is mail.MyDomain.com I ...
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G-Mail SMTP Service accounts

I'm setting up a google workspace for my company as we want to fully migrate our mail system to google. Part of this is obviously creating al mail boxes, aliases, etc. Now we currently have some mail ...
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Setting up Postfix relay server through google apps

Image description of out environment we have Multiple servers and different services are hosted on them, we are using G-suite enterprise hosting so don't own our own server. as we have to send ...
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postfix enable sending bounce messages to sender

I currently trying to enable sending mails to the sender then the mail is undeliverable. For example the mx1.my.domain which is the MX for my.domain recieves a mail for person1@my.domain: 868942A: to=&...
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Adding SMTP server to binding domain

I am using Windows server 2012. We have a binding on one of our sites that behaves like a subdomain, for example: Site : domain.com - x.x.x.9 Bind: sub.domin.com - x.x.x.10 binding points to another ...
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1answer
114 views

ICMP “Port Unreachable” when sending email

Since several months I have sporadic problems when I send emails. With tcpdump I finally found out that I'm getting "Port unreachable" messages from what seems to be my email provider, ...
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SMTP Untrusted TLS connection still sending emails

When sending mail from my client through a mail server that is then using AWS SES as a mail relay I'm seeing this in the postfix log as each message moves through: smtp: Untrusted TLS connection ...
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Can mailings be sped up by using multiple connections to SMTP servers?

We use a mail server that runs Exim to send mailings to our clients. Sendblaster is used to connect to the server and send the emails to a list of clients. Currently we use two instances of ...
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How does Postfix define an unlisted recipient or sender?

Postfix's documentation defines smtpd_reject_unlisted_recipient (default: yes) as Request that the Postfix SMTP server rejects mail for unknown recipient addresses, even when no explicit ...
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How do you instruct Postfix to use SMTP over a different port? [closed]

I'm operating a Postfix server, and my local network has port 25 blocked. I've tried everything I can to in order to get port 25 unblocked - no dice. Unlike this I don't want to proxy my data. (Haven'...
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1answer
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Downloading IMAP/POP3 emails on a remote server to a local mail server

I need to setup a local server that will download email (IMAP or POP3) from remoteserver e.g gmail or webmail, to a local server. Such that users can have structured access (either via mail client or ...
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48 views

Postfix relay based on source IP address

I have 2 applications currently using separate Postfix to work. I want them to use a single Postfix. One of the application has a relayhost to a different server and that is configured. The other ...
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Postfix should not use some smtp_check_headers for local delivery

For a postfix server i need to relay to an other server based on the subject of the email. This is working perfectly. However it also works if the mail is send to the same domain. The rules i have: /^...
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113 views

Set Postfix myorigin to the domain that sent the email for multiple domains (SMTP Relay)

I have a Google Workspace account that has multiple sites running on one user. I have aliases setup for gmail. I've setup a Google Workspace SMTP Relay to send emails from my linux server for systems ...
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Postfix via Gmail SMTP Error with no cause

I'm trying to configure POSTFIX to send emails via smtp.gmail.com, without any success. Iv'e tried following these two tutorials: https://www.endpoint.com/blog/2019/04/30/postfix-gmail-forwarder https:...
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Set Postfix - Envelope-From - Return-Path

Servus Community, I maintain a send-only Postfix server for sending contact forms from multiple hosted wordpress instances. The problem I've been experiencing for a while now is the envelope-from and ...
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3answers
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How exactly does SMTP authentication work?

I am poking around with SMTP with the hope of getting a better understanding of how it works and I am not sure I understand how authentication works and what controls who can send a message using an ...
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Client SMTP Submission on IIS

I've got 2 IIS servers: "Local" IIS" that runs on my network and "Remote IIS" located on other network. Both IIS servers have exactly the same application installed used to ...
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37 views

My Postfix server can't send emails to cpanels (Where Port 25 not supported)

I'm getting this error to=<email@email-address>, relay=serverip:25, delay=16, delays=0.38/0.01/15/0, dsn=4.4.2, status=deferred (conversation with serverip timed out while receiving the initial ...
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1answer
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Configure postfix to send via IPV4 but receive using both IPV4 & IPV6?

Is it possible to configure postfix to send via IPV4 only but receive using both IPV4 & IPV6? My server, running on AWS Lightsail, now can have an IPV6 address. The address is relatively static (...
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1answer
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Postfix - relaying specific email addresses within a mydestination domain

Having some issues trying to get something working on postfix. That is, I have a domain abc.com which is a destination domain on my postfix server 1.2.3.4, it hosts mailboxes for addresses in this ...
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SMTP server not sending mail

I've acquired a Windows 2019 virtual server at work and have setup an SMTP server which is running and the FQDN is valid etc., all seems to be setup correctly according to a few guides I've followed. ...
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3answers
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How can I test a SMTP server?

I received SMTP server information and credentials and want to test if they work. How can I easily test a SMTP connection on Linux using the command line? I know I can do this via telnet / openssl but ...
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2answers
135 views

Delivering smtp mail from postfix to exchange and online exchange problam

I have a very strange problem with one server01 its smtp notifications mail. My scenario: server01 sends mails over postfix to local on-prem exchange server. That mail is correct with to: address, ...
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2answers
1k views

Sending emails with SMTP Relay on Office 365 via Azure VM

I am trying to resolve the issues around Azure and sending emails via Office 365 SMTP Relay (Connector), but the help online doesn't resolve the problem. I have a PowerShell System setup on Azure ...
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My postfix is used for spamming [duplicate]

I need your help. My postfix is sending spam mails. I checked my main.cf and it should be fine. In the following a snippet of my mail.log Jan 3 22:35:41 mail postfix/pickup[104179]: 866352963F01: uid=...

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