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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34 views

Exim:Use specific smarthost for certain recipient domain only

I'm looking for solution for the case described below. I've to send mail to some domains (hotmail, outlook) via smarthost, because of blocking my server's IP (Hetzner) on side of Microsoft. Key ...
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postfix smtp submission using tls not working

I m trying to set up a mailserver with dovecot, postfix, and sasl using dovecot without success. My host is a centos 8.Smtp submission on port 587 is not working. Imapsecure is working. If i try to ...
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Configure Postfix to use Mailgun - Fails within same domain sending

The Configs We did the usual main.cf (postfix) relay/sasl entries: # Amavisd + SpamAssassin + ClamAV # content_filter = smtp-amavis:[127.0.0.1]:10024 # Concurrency per recipient limit. smtp-...
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What could cause RECP TO to be slow

I've a postfix server running with mailu, and for some reason, RCPT TO takes a long time to return OK. Connected to mail.example.com. Escape character is '^]'. 220 mail.example.com ESMTP ready EHLO ...
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Postfix SMTPD and recursive virtual_alias_map lookups

I'm building a virtual mail setup with Postfix, but I'm having issues with virtual_alias_maps. The documentation explicitly says its recursive, but I can't for the life of me get further than the ...
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Does Gmail require TLS for receiving mail?

I am currently working on sending e-mail in PHP directly with stream_socket_client(). This is working pretty well so far. I am able to send HTML e-mail with a DKIM signature that passes all the tests ...
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MTA rejects mail, returns 554 error although rDNS is set

I have a docker-mailserver container running fine except that mails aren't delivered to GMX and web.de which are both german mail providers belonging to the same holding company. I assume they have ...
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49 views

Do I have the right IpTables here? I cannot send but I can receive

Setting up a mailserver and I've taken steps to secure it. One of the steps is to have a set of IPTABLES rules From you can see, I've set all the policies to DROP, even the OUTPUT, I think that's ...
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What should be the SMTP server when using the Amazon MAIL FROM domain?

I have set up a MAIL FROM domain with Amazon SES by following their instructions: https://docs.aws.amazon.com/ses/latest/DeveloperGuide/mail-from.html They have verified that the DNS records were set ...
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1answer
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Awstats + Postfix logs - no senders/recipients?

I am trying to configure awstats (v7.6 from repo on Ubuntu 18.04) to process postfix log files. But I don't have much log data to work with. Awstats is reporting that it has processed the data and the ...
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1answer
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Yahoo mail always sending 250 code for SMTP rcpt

As the title suggest yahoo.com gives back a 250 codefor good and bad e-mail addresses, i.e for one's that exist and those that don't. Is this just Yahoo policy or am I doing something wrong? If it ...
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Send mail using my own SMTP Server

I have windows server 2019 configured in AWS . Installed SMTP server role. Now , i have a simple mail client which i downloaded from below github link. https://github.com/CodeCowboyOrg/...
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Exchange 2016 on server 2012r2 port 25 closed

Port 25 won't open anymore since a few days. I don't know what exactly preceded it, maybe server crash or update. /owa and /ecp work and I can also connect with Outlook, but I can't get any mails. I ...
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Getting postfix to log to a file on docker

I have created a docker image based on Ubuntu 20.04 with postfix and dovecot. I also installed syslog-ng in hope to solve my problem, but it didn't work. Thing is, I want to use fail2ban to prevent ...
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Use alternative SMTP provider for Gmail/Gsuite

Does GSuite or Gmail have a configuration option where you can use the native Gmail UI and send email from a different SMTP server? I want to send emails from the same email address as the Gmail ...
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How does reverse DNS add security? [duplicate]

There are plenty of good answers here about how reverse DNS works, but why is it used? It seems that all reverse DNS proves is that the person sending the email has access to the DNS records for the ...
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Valid domain rejected by James

For some reason suddenly I’m getting that error on James: DEBUG 09:32:35,635 | james.smtpserver | Id='1973954440' User='' Unknown domain ABC so reject it DEBUG 09:32:35,635 | james.smtpserver | Id='...
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Exchange server receive size limit

My Exchange 2016 server is rejecting an incoming SMTp message with error: Remote Server returned '550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization' I confirmed that ...
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122 views

exim. how to stop sent bounce message

I have smtp server exim. I want to forbid to sent bounce message if the e-mail came to a non-existent address. I added to the beginning of acl in the config: begin acl acl_check_rcpt: ...
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Mail-in-a-Box SMTP Authentication Failure

I have successfully set a mail-in-a-box (MIAB) on Ubuntu 18.04, I intend to use it as an external SMTP solution. However I am having issue with SMTP authentication. Scenario; Server: box.example....
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2answers
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How to apply HTML layout template to email using EXIM?

My goal is to apply a standard, branded layout template to all emails when sending (on the server, not the client). I have been googling this topic and not found any resources specifically addressing ...
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I tried postfix restart, said service isn't running. Yet I am on my working mail server? (cent os)

So I am not sure what I am doing wrong. This all started with the need to let others from outside our network access the SMTP to send email from offsite. So I had in /etc/postfix a check_clients ...
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1answer
48 views

Is this configuration for email is secure?

I am using nodemailer package with node.js to sending mails, and I am not sure about security. The host I've received is working only with this configuration (also with port 587): const transporter ...
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1answer
76 views

Is there a way for an SMTP server to respond that a user has moved to a new address?

Is there a way for an SMTP server to tell an MTA that a user has moved to a new address? There are many SMTP return codes, including for common situations like Mailboxes being full, the address not ...
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SMTP-Docker not sending emails, what am I doing wrong?

Please bear with me, as I only started out with Docker a couple fo days ago. I created a brand new VM with CentOS 7 in our ESXi server. Setup Docker and Portainer with no issues. I wanted to create ...
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Cannot send TLS emails

I just migrated to a new server. With it I have problems sending TLS emails. I made a php code to test it as bellow: <?php require 'PHPMailerAutoload.php'; $missatge_complet = "HOLA"; ...
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1answer
21 views

SMTP server not sending DSN

Is the outgoing smtp server expected to notify sender of failure in upstream transfer giving this scenario?: User A tries to send email message via his Outgoing SMTP (A-SMTP) server to recipient B. ...
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1answer
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Inaccessible SMTP server, no error from mailer daemon

I would like to know what behavior should I expect, when I try to send an email to an address where the corresponding server has no working SMTP daemon instance running (for whatever reason). My ...
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1answer
108 views

Exim + Dovecot sending or receiving an email occurs the error: Unknown user

I'm running a mail server with CentOS 7 + Exim 4.92 + Dovecot 2.2.36 and RoundCubeMail as web interface, and have the following problem: when I send to or receive from emails which is not admin@ or ...
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47 views

Postfix server sends mails properly, but not recive them

I set up my mail server with Webmin/Virtualmin with Postfix couple days ago. Server lives on EC2 instance. Everything was working just fine. Mails were being send and I recived them properly as well. ...
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SMTP Server and HTTP Server on a single VPS [closed]

I have a VPS (CentOS 7) with an Apache HTTP server already running on it, with its own domain. But, I also want to send emails from that domain, so that I have a website called example.com and I can ...
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Relaying Office 365 mail to Postfix

I am setting up a system that relays all mail from Office 365 to a Postfix server, which fixes the headers before sending on. It is working by creating a connector in Office 365 to "partner ...
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Postfix via relay server and LMTP configuration for incoming delivery to local mailboxes

I'm trying to set up something like a configuration below for a local delivery (to force local delivery via relay server): Dovecot ---------------> Postfix --> Relay Server -┐ Dovecot <-- ...
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ERROR smtpserver: Socket to hostname (x.x.x.x) closed remotely. java.net.SocketException: Connection reset

Haproxy smtpchk is flooding errors in smtpservers.log. The option “option smtpchk” in the (haproxy.cfg) SMTP backend is causing the below error at every check. ERROR smtpserver: Socket to hostname (x....
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Setting up new server. Strange entries in /var/log/mail.info

I'm setting up a new webserver and noticed these lines in my mail.info appearing every 5 minutes. Anyone know what is causing this? Mar 30 17:45:02 enterprise dovecot: imap-login: Disconnected (...
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2answers
56 views

Wordpress/Easy WP SMTP Error Sending TLS Secured Mail to Exchange 2016 On-Prem Server

I have a non-domain joined Windows Server 2012R2 web server hosting Wordpress with the Easy WP SMTP plugin in our DMZ. It is supposed to send email to our internal Exchange 2016 server for things ...
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1answer
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Sending emails via SMTP with postfix

I have a VPS in which I have installed and setup postfix as a send-only mail server. This command here works perfectly fine to send mail echo "This email is a test" | mail -s "This is a test ...
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BDAT mail command in Postfix

I've been trying to research the BDAT command, specifically in connection with Postfix. I wasn't able to find a huge amount of information and I have 3 questions. (1) As far as I can tell, Postfix ...
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682 views

Roundcube Webmail

I have an extremely frustrating situation with Roundcube Webmail: A client of mine has asked for a WordPress server and a full service email system. The email system is registered already, and ...
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Exim delivers mail successfully but keeps it queued for no apparent reason. Recipients receive mail multiple times

I recently upgraded my exim4 mailserver from Debian 9 to Debian 10. Since then I have the issue that random emails get queued although no apparent error occurs and the emails successfully deliver. But ...
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Can send smtp mail using go/smtp on my localhost. But when running behind a apache2 ProxyPass on a gcp computed server, I get a 534 error

On my Localhost when running my go program and sending an email through it theres no errors and it works great. But when running the same go program on my server and checking the error logs, I seem to ...
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1answer
113 views

nullmailer - Diagnostic-Code: SMTP; 550 5.1.0 <root@external_email_server.com> sender rejected (497)

What did I miss-configure to be getting MAILER-DAEMON errors? (I was trying to keep this post short, but it got a bit out of hand.) I am setting up an email alert system for when my RAID1 should go ...
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39 views

Exchange 2016 connectors fail

Do you know how I can resolve The problem below? This scenario was normally working few months... Exchange 2016 SMTP client is trying to send email by port 25 using TLS and Basic auth. Recive ...
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1answer
134 views

Exim4 Rejected RCPT: Unrouteable address when using data lookup

I'm trying to redirect emails originally sent to hello@example.com, to the mrxxx@example.com. I have aliases file: hello: mrxxx@example.com And the following routers: local_router: driver = ...
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3answers
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How to set MX record so that delivery results in temporary failure

I am moving an SMTP server from a host to another. In order to make things as simple as possible for me (and since I don't care if email are delayed a few hours), I would like to adopt this strategy: ...
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Postfix How to send Email to Hold que based on response code?

Good Morning, I am looking for a postfix configuration that will send all emails that have a return status of status=SOFTBOUNCE to the HOLD queue, any help will be greatly appreciated. Intail research ...
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1answer
121 views

I just sent an email in a loop for 5 minutes

A bug was in my cron code. I just sent thousands copy of the same email in a loop during 5 minutes to 24 people. All my smtp responses were ok (like Google ones were "gsmtp 201"), meaning that all the ...
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21 views

Phishing campaign can send to webmail, not sure where domain is blocking it

I'm trying to run a phishing test campaign for my company with gophish, a domain I bought, and hmailserver. I can get the sending profile to send e-mail to my personal gmail account, but it's not ...
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1answer
14 views

SMTP DKIM for 1 add-on domain on 2 servers

Is there a more practical way for SMTP DKIM signing for a VPS server that has a parked domain but does not host the content other than private key copying? I have looked all over Server Fault but ...
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2answers
49 views

Security when SMTP Relay is allowed from the Private Address Blocks

Is it safe to allow SMTP Relay from the private address blocks? 10.0.0.0/8 127.0.0.0/8 172.16.0.0/12 192.168.0.0/16 My gut feeling is that it's probably OK, however I'm not sure if that will not ...

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