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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.

492 questions with no upvoted or accepted answers
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IIS SMTP TLS encryption issue

I enabled TLS in IIS SMTP Virtual Server with a self-signed server certificate. Made sure that the certificate has the FQDN of the server. Checked the TLS encryption checkbox in Virtual SMTP > ...
4
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1answer
959 views

edge server 2016 not receiving email, blocked ports?

I am trying to setup a new Exchange 2016 implementation. I can send emails but I cannot receive them. So far, the emails don't get rejected though I suspect in a few days, they will start to bounce ...
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241 views

How can I explicitly disable TLS when sending to one specific recipient?

I have a SendMail 8.14 server deployed in the middle of an SMTP workflow (Outbound mail looks like Exchange -> SendMail -> Appliance -> Internet) I have TLS configured for the first three hosts. ...
4
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1answer
5k views

Exchange 2003 mail non-delivery (NDR), spam activity? events 7002 & 7004

Windows Server 2003 Small Business Server SP2 Exchange Version 6.5 (Build 7638.2: Service Pack 2) This network has been neglected and has been having email problems for years and was on many ...
3
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0answers
118 views

Why is Exchange 2010 SMTP not rejecting external messages to internal-only groups?

TL;DR: How do I make sure that the SMTP server doesn't accept external messages for distribution groups that are set to require authentication? I have an Exchange 2010 server that has multiple ...
3
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1answer
182 views

Is it possible to change sendmail behavior on “Host unknown” errors?

Sendmail 8.14.4 I had DNS issues resulting in a DNS server thinking that a hostname wasn't available (when in fact, it was available). That resulted in the following delivery log entry in sendmail: ...
3
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0answers
459 views

Don't send outgoing mail via Spamassassin

My e-mail server is running Postfix 2.11.3 on Debian 8.7 (Jessie) with Spamassassin 3.4.0. I realized that my outgoing e-mails are also being checked for spam, which not only seems to be unnecessary ...
3
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97 views

Combating a persistent spam list

We use Office 365 as our primary mail provider. We have an internal mail server that we use for relaying things like reports from our SSRS, scan to inbox for old scanners, etc. It is an IIS SMTP on ...
3
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1answer
69 views

SMTP authentification request transfer to another SMTP

I'm having an issue that's above my competence level. As we're working on improving the security measures that are in place in our network, we found (among others) one flaw that we have no idea how to ...
3
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0answers
101 views

Postfix STARTTLS works in LAN but not externally

if I connect in LAN on port 25 to my mail server, it offers STARTTLS telnet mailserver.com 25 Trying 192.168.0.x... Connected to mailserver.com Escape character is '^]'. 220 mailserver.com ESMTP ...
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hMail Server SSL Certificate Verify Issue | TLS/SSL handshake failed

I will tell you my situation step by step and ask me any necessary questions and help me to fix hmail certificate issue. First of all : 1- i am using a windows server 2008 - r2 2- latest hmail ...
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0answers
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How to detect SMTP AUTH attempts in Fail2Ban?

I have a Fail2Ban jail that monitors failed SASL authentications to my Postfix SMTP server. When this occurs, /var/log/mail.log contains these three lines: postfix/smtpd[32591]: connect from unknown[...
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2k views

Outlook.com rejects: 550 SC-001 (BAY004-MC5F13)

I am operating a cluster of 3 dedicated machines for a webapp, each of those uses sendmail as MTA. Hostnames are node1.domain.com node2.domain.com node3.domain.com Unfortunatelly outlook.com rejects ...
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0answers
1k views

nullmailer swaps sender and recipient

I want to send emails from my server through external mail server. So I installed nullmailer as one of simpliest MTA in Debian 7 x32. My /etc/nullmailer/remotes: smtp.example.com smtp --user=sender@...
3
votes
1answer
363 views

Exchange 2010 is trying to relay messages for delivery

I am using Exchange 2010 on premises. I am in the process of setting up a SMTP proxy that will receive all messages coming into the office, log them, then forward them to my exchange server for local ...
3
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391 views

How to identify the user/computer that is relaying spam through a mail server?

For the past couple of days, at certain intervals, a huge load of email is dumped on my Exchange 2003 server and relayed out until it gets blacklisted everywhere. Nothing like this happened for many ...
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3answers
267 views

Mail relays or SMTP services for use in code

I'm looking to start using an SMTP or mail relay service. I've found quite a few out there, but I'm not sure if there are advantages to one vs another. The only requirements I have are: can send "...
2
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73 views

Sendmail - convert 500 fatal errors to 400 temporary errors - possible?

I run a couple of email relay hosts at work. A number of customers use ProofPoint as email washers, so their MX record in DNS is something like mxa-002d7b01.gslb.pphosted.com which washes the mail ...
2
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1answer
45 views

Mail blocked from Windows Server 2016, but not since 2008

Good Morning: I'm running exactly the same script from two different virtual machines: The first in Windows Server 2008 R2 The second in Windows Server 2016 Features The SMTP is an external ...
2
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1answer
395 views

Forwarding emails from postfix to exchange server?

I have some web application which is used as a webmail client to exchange. I can pull emails from exchange server via IMAP, but problem is at sending mails. Application is using MSMTP client to send ...
2
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0answers
71 views

Connecting to a external exchange server via linux/php?

We have an SMTP relay available that we are using on windows servers. [mail function] ; For Win32 only. ; http://php.net/smtp SMTP = email.relay.url ; http://php.net/smtp-port smtp_port = 25 ...
2
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1answer
83 views

Reject Exim authentication attempts based on username

Is it possible to set up Exim so that, based on the username passed along to it, it can reject an authentication attempt before it will try to do a password lookup for that username? I've done similar ...
2
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1answer
157 views

Postfix gives error in maillog: maps_find: smtp_generic_maps: log: not found

I have changed the default FROM address of Postfix, from root@example.com to log@example.com I can send the e-mails fine, but when I check the maillog file I then see some "not found" errors. /etc/...
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89 views

Prevent postfix from trying secondary MX after soft bounce from Google MX servers

My local SMTP relay is finding it increasingly difficult to deliver mail to my G-Suite groups and users. The volume is not very high, but Google enforces rather low limits on incoming e-mail from ...
2
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1answer
2k views

Exim not Listening on port 465 or 587 for TLS connection

I am configuring Exim on a Ubuntu server to send and receive mails via TLS. Followed many guides which shows on how to configure Exim with TLS but still my Exim doesn't listen on 465 or 587 Exim ...
2
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305 views

With a period/dot in the name part of the address, Domino 9 SMTP won't accept incoming mail

Summary: Receiving mail to username@foo.com works, but user.name@foo.com doesn't. On an IBM Domino 9.0.1, a proper Global Domain document exists for the domain foo.com One user has two email ...
2
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1answer
54 views

“Fetching” SMTP connections

I'm struggling to word this question so please bear with this preamble. We use a product called Serv-U from Solarwinds as an sFTP server as it has a gateway feature I find really handy. The server ...
2
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1answer
2k views

SMTP load balancing with remote host's IP passed through to SMTP servers?

I'm attempting to build a load-balanced SMTP cluster. The mail servers already exist and run Exim 4. Initially, I looked at using Nginx to do the load-balancing, however on the test system all the ...
2
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2answers
617 views

Exchange 2013 Banner

We have an exchange 2013 server that is failing a reverse SMTP Banner Check: 220 [Internal IP] ESMTP Smtpd; I have gone into our exchange receive connector for the internet, "Default frontend ...
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0answers
119 views

Postfix doesn't send email, only receive

I recently install on my Debian Server the PostFix + Dovecot + Mysql, everything works fine, but I cant send email, I receive the error on the log NOQUEUE: reject: RCPT from unknown[##.4.##.41]: 454 ...
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58 views

vCenter email notification has a semicolon/SMTP does not recognize it as a valid email address

Messages from vCenter has this header info: Received: (from root@localhost) by (8.14.3/8.14.3/Submit) id u92F2su5032029; Sun, 2 Oct 2016 15:02:54 GMT Date: Sun, 2 Oct 2016 15:02:54 GMT ...
2
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1answer
3k views

External recipients in distribution group not receiving emails

In Office365, we have a distribution group, group@company.com, set up with the following members: internaluser1@company.com internaluser2@company.com externaluser@external.com (@gmail.com, for ...
2
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0answers
205 views

Postfix permit localhost use plain login

I have postfix 2.11 setup on Debian jessie with Dovecot SASL and I require encrypted login mechanism to send mail via smtp. For this purpose in the main.cf I've smtpd_tls_auth_only = yes option set. I'...
2
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1answer
103 views

Catch incoming email and then deliver to original recipient on sendmail

in the company I work for there are a user that is making bad use of the email, but to have evidence of what he is doing we need to intercept all the incoming email to him and all outgoing email from ...
2
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0answers
728 views

Does Google require TLS on port 587? Exchange 2010 SMTP has mail sent to GMAIL backed up in queue

Exchange 2010 SMTP has mail backed up in queue. Any email sent to Gmail sits in the queue while any email sent to another personal domain which has email filtering enabled errors, "asp.reflexion.net ...
2
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0answers
601 views

Getting “5.7.1 Unable to Relay” intermittently on mails sent to Exchange 2013

I have a helpdesk system that sends mails through the local exchange server. Until a few days ago, I never had issues with it. For the last week we have started getting complaints about missing ...
2
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0answers
2k views

When does Postfix not perform lookups in virtual_alias_maps?

I'm having a real pickle of a problem: I have a Postfix 2.6.6 / CentOS 6 server that's set up to forward mail from specific aliases to specific destinations. This is done through a mysql ...
2
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1answer
4k views

Configure Citadel to be Used For sending email using smtp

Sorry for this foolish question, but I have less knowldge about servers. So bear with me! I have configured Citadel as directed in linode documentation and can login using the front-end for accessing ...
2
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2answers
494 views

how to Dedupe email messages in exim mail server (Linux)

If a User is listed in multiple aliases or multiple mailing list or groups a message is sent to more than one of the aliases, mailing list or group the end User will receive multiple copies. How to ...
2
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1answer
2k views

Exim SMTP Smarthost Setup

I used these settings to set up exim to use gmail as a smarthost, which worked. However, I don't seem to be able to use these settings against other smtp servers, such as Yahoo or Fastmail (both with ...
2
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1answer
897 views

SMTP Event Sinks in Windows 2008 R2

We use a 3rd party software to send Bulk Emails. The software does not provide options to add Email addresses in BCC. However, as per Compliance Rules, it is necessary for us to add a BCC address to ...
2
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0answers
976 views

Stop IIS SMTP Server from sending “Delivery Status Notification (Failure)”

I have set the BadMail directory and the 'Send copy of Non-Delivery Report to' fiels is empty but, somehow I am still receiving the failure messages. Is the a way to stop the failure messages?. I am ...
2
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0answers
35 views

I need to set-up the blocked machine to relay to the unblocked machine using a different port

I have two Windows Server 2003 machines sitting in a network. Server B has port 25 open and can relay emails to the local network's smtp server. Server A does not have port 25 open. How can I set it ...
2
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0answers
465 views

Forcing IIS virtual smtp server to verify outgoing TLS certificate

I am in a situation where a web application is using the IIS virtual SMTP server to send out email. The IIS virtual SMTP server is then configured to send all mail out through a smarthost, over TLS ...
2
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3answers
378 views

Trivial Issue with ASP.NET 1.1 and SMTP

The server is running on: Windows Server Standard on SP2 IIS 7 with ASP.NET 1.1 IIS 6 for SMTP The server hosts many websites running ASP.NET 1.1. These websites use the built in SMTP server on IIS6....
2
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1answer
224 views

Is is a good idea to put SMTP Shadow replication on the same VLAN as DAG replication?

We have a VLAN for DAG replication, Recoverpoint (SQL Data), and right now SMTP Shadow replication is going over with the production traffic. Should shadow replication be limited to the site? Should ...
2
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0answers
285 views

How can I change the default email address format type for replies on blackberry?

Exchange 2007 BES 5.0.x Hello all, I'm trying to help a colleague with a technical issue. I apologize in advance for not having all of the information. I'm looking for some advice on where to ...
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3answers
3k views

Domino always server fails to send SMTP email at first attempt

In our logs, we find the below: Router: No messages transferred to example.com (host mx.example.com) via SMTP: The server is not responding. The server may be down or you may be experiencing network ...
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49 views

Windows Server 2019 SMTP Server - Email Stuck in Queue / Not Being Released

I've recently upgraded a number of servers from Windows 2008 R2 to Windows Server 2019. 2 of the servers require SMTP which I have installed on both, however, 1 server works as it should and the 2nd, ...
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17 views

Windows Server 2012 Blocked Network Activity

I am trying to telnet some other machines from my Windows Server 2012 computer, and also to test the SMTP connection using telnet again. Although I have created all the required Windows Firewall ...