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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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Is a mail subdomain necessary?

I have just taken ownership of a domain which had a couple of associated email addresses. I have left the mail boxes with the previous host, and so have been looking at updating the MX records in my ...
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1answer
23 views

SMTP MTA to MTA authentication

I still have trouble understanding how a receiving MTA authenticates the forwarding MTA. I imagine an email that is forwarded by domain A's MTAA to domain B's MTAB. Steps to take by MTAA: Find MX ...
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Postfix 'too many errors' after many RSET commands

I have a client who is complaining that their invoice emails are not all being sent out correctly. As far as I'm aware their invoicing software is designed to send emails directly. Looking at a ...
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1answer
34 views

Postfix bounce when unable to validate TLS option

I'm using postfix as mail transfer agent on my mailgateway to send and receive emails. Because I'm communicating with sensitive information I'm using the tls options to validate the receivers mx. He ...
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Server 2012 R2 SMTP service not sending mail to non TLS servers

We have SMTP virtual server on server 2012 R2 server. I have configured it to use TLS connection. We do have real sertificate etc. Everything works fine except mail that is going to mail server which ...
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2answers
70 views

One domain with multiple MX servers and forwarding instead of erroring

I have a domain with few hundred email addresses. We are migrating our hosting to multiple ISPConfig servers. My problem is if someone sends email to email@domain.example and if the email does not ...
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1answer
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Postfix is appending myorigin to non-FQDNs despite “append_at_myorigin = no”

I have postfix and a local LMTP server running. In my main.cf, I have append_at_myorigin = no. When I run postconf|grep append_at_myorigin I get that this value is no. But for some reason, postfix is ...
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1answer
25 views

Some users seeing unformatted emails with winmail.dat files while others aren't

We have a hosted BitBucket instance that is sending emails via SMTP through Exchange 365 to external users. Some of those users are seeing the properly formatted emails when looking at them in Gmail. ...
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1answer
20 views

Problems with certificate in Exchange 2016

We have just installed a new mailserver, with exchange 2016. We need to have our wildcard certificate assigned with the smtp service in exchange. I edit the certificate in exhange EAC, tick the ...
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2answers
24 views

Multiple SPF entries in same or separate TXT records

I want to use a mass mailing service, e.g. sendgrid, mailgun, etc. And so I must update my zone file to include the correct SPF records. Suppose my domain is example.com. My DNS provider ...
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1answer
41 views

Postfix 451, 4.3.0 : Temporary lookup failure

we've followed the guide HERE to configure a Postfix. After sending a message via telnet we receive the following error: Oct 8 18:52:01 mail postfix/smtpd[3719]: connect from unknown[10.10.10.9] Oct ...
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Postfix header_checks in psql

In Postfix is it at all possible to perform header checks based on a PSQL lookup? I haven't found anything explicitly saying you can...but also haven't found anything supporting it. Ideally, I want ...
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Do you need to use IMAP to read bounced emails?

I'm writing a send email app in Laravel which will use my own email servers. Many apps read an IMAP inbox to log the number of bounces a user might receive- using some cron to check and delete bounces ...
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1answer
65 views

Why smtp server can not be telnet?

https://www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email/ I am following the above instruction to telnet an email server of gmail. But I got an error. ...
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Email issues with MT4 [duplicate]

So I have a hedged trading strategy which pings me a trade confirmation email via it’s built-in SMTP server. Because there are two trades (a buy and a sell trade), there are two emails which are ...
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1answer
32 views

iptables block outgoing on port, allow selected IP's [duplicate]

Debian 7 iptables v1.4.14 (there are no rules) Need to block all outgoing connections on ports 25,587,465 and allow only on specific IP's. What I've tried: iptables -A OUTPUT -p tcp --match ...
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Is there an option for nginx mail module to use STARTTLS on upstream servers?

I'm currently setting up a mail cluster for sending mails. To avoid sending limits of various providers (like gmx) I decided to setup a smtp loadbalancer using nginx and multiple postfix servers as ...
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38 views

Where does sendmail get its user authentication information?

I set up a new remote CentOS email server using sendmail and dovecot. I am able to receive mail into mailboxes but can not use SMTP to send. Trying to login by hand using # telnet mail.steelydev....
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13 views

Why is my firewall rule being ignored?

I'm having difficulty getting the firewall on a Draytek Vigor 3220 to pass incoming connections to port 25. I've set a rule to pass TCP packets from WAN to LAN from any source IP address and port to ...
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1answer
33 views

iredmail - Emails go out but don't come in

I setup an iredmail server so that my website can send registration emails and all that sort of thing. Problem is, it can send mail just fine (And even inbox) but it can't receive. Port 25 is open, ...
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2answers
436 views

554+5.2.0+STOREDRV.Submission.Exception:SendAsDeniedException in IIS SMTP Relay When Scanning to Email from a Sharp MX-M364N

I am getting the following error in my Windows Server 2012 R2 - IIS6 - SMTP Relay logs when I send a scan from a Sharp MX-M364N copier: 2018-09-25 20:28:54 40.97.132.2 OutboundConnectionResponse ...
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1answer
29 views

Postfix can't send or recieve emails

I have setup PostFix that is also running with dovecot on my server. My server is running Ubuntu 16.04. I cannot send or receive emails from squirrelmail that is also running on my server and it ...
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1answer
76 views

Postfix auth issue

I'm currently facing auth issue. When I'm trying to auth via telnet, I face an issue "535 5.7.8 Error: authentication failed: authentication failure" I use password and login the same, as I use for ...
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1answer
58 views

EXIM SMTP allows to send mails without login / authentication via telnet to any domain

I'm ashamed, but I have to ask for help. My server is being used for sending spam, I've found out I can simply connect with telnet (edit: from any server in office, home and even directly from CMD/...
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1answer
37 views

Does email from IIS SMTP get rejected?

A client has been using IIS v6 SMTP over Windows 2008 R2 for many years to send out automated server notifications. Their apps use Blat to send through localhost with no authentication. Email seems to ...
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1answer
49 views

How to send encrypted message using postfix?

I have some application on ubuntu 18.4 vps. i can send mails using postfix but gmail says it is not encrypted. postfix config file is: # See /usr/share/postfix/main.cf.dist for a commented, more ...
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2answers
137 views

iDRAC 9 Enterprise SMTP alerts w/Office 365

I'm running a Dell PowerEdge T440 with iDRAC9 Enterprise. I'm attempting to setup SMTP alerts using Office 365. I have been unable to successfully send a test e-mail at all. I receive the error: ...
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0answers
18 views

Insert several servers IP via txt/csv under SMTP on IIS 6 (Windows Server 2012) via shell/vbscript/anything [duplicate]

We would like to import several servers authorized IP's to send mails to the relay field on IIS 6 (WS2012). Do anyone have a viable way to do it? Many scripts were tested, none successfully.
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1answer
71 views

Unable to block port 25 on server

When I scan my server using nmap $ sudo nmap -sS IP.ADDR.OF.SRVR, I see a line with 25/tcp open smtp. This is despite the fact that I'm not running postfix, exim or any other kind of mail server ...
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1answer
65 views

Mailgun/Postfix: Relaying Denied

I have checked the other threads on here and none seem to resolve my issue. I am trying to relay my outgoing emails from Postfix to Mailgun via SMTP. My server is also running Plesk. My Postfix ...
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0answers
17 views

Multiple Received headers with sendmail php

I just initialized sendmail and I'm sending some test mails to my personal email address with a very simple PHP script. I noticed something odd, here: Received: from mydomain (MYIP.ip98.myhostname [...
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1answer
39 views

Set up a smtp (mail) delivery server

this question could probably be simple but frankly I don't know exactly what it is. This is my scenario: I have multiple devices like: UPS, router, switch,... and they all have option for me to ...
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How to correctly set local_recipient_maps for Postfix

I really don't understand enough about how each of these pieces fit together. I followed the guide at http://www.shisaa.jp/postset/mailserver-1.html a few years ago, but I need to stop the backscatter ...
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0answers
52 views

Postfix transport based on source IP address (with or without relayhost)

We have Postfix relay server running on centOS 7.4. Restricted source IP address by mynetworks cidr mynetworks = cidr:/etc/postfix/allowlist.cidr Now, I like to configure, some of the source ip ...
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1answer
47 views

Linking GCP Compute Engine with Google Suite SMTP Relay Service

Recently we want to connect GCP Compute Engine with Google suite email service. at this documentation told that Google Compute Engine does not allow outbound connections on port 25. By default, ...
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1answer
22 views

Optimizing delivery with limited outgoing connections

I have several VPSes to a provider which recently started throttling outgoing SMTP connections to prevent spam. While this is not such a big issue, sometimes mails gets delayed for obvious reasons. ...
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1answer
89 views

Email server with no smtp connection

Ubuntu 18.04 on Google Compute Dovecot + postfix I figure I should be able to connect to a port other than 465/587, and since I can relay all email through google there should be no issue with this ...
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1answer
86 views

How to recover domain name from previous bad SPF record?

TL;DR: We had SPF too permissive (+all) and spammers used this to send tons of spam "from" our domain. We restricted that to ~all and added DMARC (not DKIM though), now other providers do not trust ...
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1answer
140 views

Postfix 2.6.6 with TLS - unable to receive emails from GMail (and a couple of other MTAs) but others are OK, why?

I've just had to look at a CentOS 6 server running Postfix 2.6.6 which was able to send emails to everyone, but could not receive them from GMail (and a few other MTAs) due to incoming TLS negotiation ...
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1answer
35 views

Sendmail relay alters recipient email?

Hello I am trying to set up sendmail on a Centos 7 server to relay mails from a local program to our main mail server. I have configured sendmail.mc with the following, mail.[domain].com is our SMTP ...
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0answers
30 views

setup Postfix gateway problems

I want to setup a PostFix mail server using gateway. I want two features. First, Mail send. MailClient ----> MyMailServer(10.0.0.2) ----> MyGateway(10.0.0.1) -----> Internet: Other MX Server ...
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87 views

Avoiding E-Mail spam filters (possibly based on originating computer?)

We recently started to send out a higher amount of E-Mails (invitations to a private event) to a select number of people. Now from some of those people using office365 for Mails, we were informed that ...
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0answers
19 views

I can't receive emails from my MT4 Platform

My MT4 platform sends emails with no issues (as per the Journal Log) so free (Yahoo, GoogleMail) accounts with no problem, but when I change the "To" email to my companies domain I can't receive ...
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1answer
28 views

Qmail SMTP receiver always delays by 66 seconds

I am currently struggling with a problem in my qmail setup, which seems to delay my smtp receiver everytime for 66 seconds. This is for most remote hosts fine, but some seem to reach their timeout and ...
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0answers
53 views

Postfix check_recipient_mx_access not working

My postfix install relays for quite a few different domains but I would like it to just shove all messages from one domain, destined for any Google MX's through the Google G-Suite relay service. In ...
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3answers
45 views

Dovecot SSL - IMAP works, SMTP fails

I'm setting up a small mail server using postfix+dovecot. When running oppenssl s_client -connect mail.myserver.com:993 (IMAP), the server's certificate is displayed and I'm able to get an email ...
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1answer
25 views

How mailchimp can sign email changing the domain and from header?

I've configured a SMPT server using postfix, dovecot, opendkim, openspf, openssl etc... I'm trying to figured out how mailchimp can send mails signed by their servers and deliver to recipients without ...
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1answer
65 views

Do I have to, and how do I setup bounce emails HELO command?

Our server has been listed several times on CBL (see this question) because it "attempted to send email without using the HELO/EHLO command". Grep'ing on HELO on Exim's logs, I found such suspicious (...
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0answers
26 views

Setup SMTP connection between mautic and iRedMail

I have set up my iRedMail on AWS EC2 small instance, now everything is working fine under port no 25, but I need to authenticate users to authenticate themselves. In mautic "to authenticate we need ...
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0answers
21 views

configure postfix to allow relaying for virtual mailboxes that are forward only

I have postifx configured as a simple mail forwarder. I have 4 virtual domains in /etc/postfix/virtual with about 10 virtual mailboxes on each which all forward to my business email address. Now, I ...