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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Postfix, saslauthd, mysql, smtp authentication problems

Trying to get authentication on my mail server (ubuntu 10.04) running but am having trouble. I have a server with postfix for smtp setup, imap server with courier setup. My postfix authentication is ...
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1answer
7k views

DKIM on postfix relay server

I have a postfix/amavis relay server, with the domain name mail.example.com. It will be a relay for dozens of VPS's, which will have domains like hostname.example.net. So i have actually two ...
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1answer
16k views

How to set exim4 to send email anywhere but only from authorised users?

Struggling to get my head around the various relaying controls in the exim4 config. I can send email from my server, I can send email from home and work (because I explicitly added suitable netblocks ...
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1answer
7k views

Dovecot - Unable to receive mail - Fatal: Plugin 'sieve' not found

Struggling to Dovecot/Postfix set up on Ubuntu 11.10, Dovecot version: 2.0.13, Postfix version: 2.8.5 I can send outbound mail using the mailx command, but I can neither receive mail or send mail ...
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2answers
6k views

SMTP 552 4.3.1 Session size exceeds fixed maximum session size

I'm having a frustrating problem with one of our clients who is running an exchange SMTP server. I have an emailing component that is written in .net and I've specifically used Mono DLL's to ensure ...
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1answer
258 views

Is there a way to “replay” a packet capture of a smtp session for the purpose of debugging?

I'm troubleshooting a smtp issue involving character-set encoding and it's extremely difficult to involve the end user. I have a packet capture of an incoming smtp session that results in problematic ...
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1answer
2k views

Exim not always sending AUTH LOGIN username/password

We are sending mail using exim (configured through WHM). With the same exact configuration, seemingly most of the time exim sends the correct AUTH LOGIN username and password, however sometimes it is ...
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2answers
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Cannot send email from EC2 instance on port 587

I have written a mail service for our flask application that uses Celery and RabbitMQ to send emails (using gmail). I have got the celery consumer and producer communicating okay but I cannot get to ...
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2answers
1k views

Intermediate SMTP server (exim), how to handle backscatter?

I have a dedicated Ubuntu Lucid box at a hosting provider that is my backup MX (running exim4 4.71-3ubuntu1.4) for domains that I have configured on an Exchange 2007 server on my LAN. So my Exim ...
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1answer
331 views

Simple, forwarding-only MTA?

I have a domain and a server. I’d like to have some e-mail addresses on the domain and I’d like to forward them elsewhere. I’d love to avoid running a full-featured MTA on the server, since they’re ...
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1answer
4k views

Exchange 2013 recipient filtering - reject after RCPT TO

According to this forum thread, exchange 2013 has a new behaviour for recipient filtering. Apparently, mails to unknown users are only rejected after the DATA-Phase, not after RCPT TO as this was the ...
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2answers
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Simple SMTP server for alias based forwarding

I'm looking for a SMTP server that will just be used to forward a few email addresses. Two requirements: Easy to install and configure on Ubuntu. Has an aliases file that is easy to automatically add ...
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3answers
15k views

exim4 to relay emails

I have exim4 installed on a Linux box. The basics work fine and I can send email from that machine without any problem to whatever email address. I also have a printer/scanner which is capable to ...
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2answers
8k views

How to change sendmail fallback behavior if TLS handshake fails?

I have a CentOS 5.x server running sendmail that is failing to negotiate TLS with SOME various recipient servers. I'm looking into it. In the meantime though, I've noticed that sendmail will NOT ...
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1answer
193 views

Hot/Lukewarm mail server setup

We have two mailservers ("dubone" and "dubdeuce"), one does all the work while the other sits idle. We want to have a setup where if dubone is busy or down, dubdeuce can accept/reject/filter emails ...
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1answer
1k views

How to choose a smarthost based on From: address in exim4 on Debian

I want to route emails with the From: .*@host1.com through smtp.server1.com and emails with the From: .*@host2.com through smtp.server2.com. For the moment, I have smarthost configured with dpkg-...
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2answers
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GitLab not sending mails

I have a Linux Ubuntu 14.04 installed on my VM. Recently I have installed GitLab 7.8.2 using the instructions on GitLab site, and encountered problems in making Gitlab to send mails. for example, ...
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1answer
2k views

Postfix SASL with Dovecot and Authenticated Smarthost

I have a bit of a problem; I have configured postfix to use dovecot for SMTP AUTH, therefore I had to specify dovecot authentication in the main.cf file. The problem is, I need to also authenticate to ...
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1answer
3k views

Exim4 require TLS for all hosts but localhost

As my webmailer does not support STARTTLS and I want to enable relaying for everyone at localhost, I would like to have Exim advertise AUTH PLAIN and LOGIN only without TLS if the connection was ...
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1answer
1k views

What does an empty AUTH EHLO SMTP response mean with MS Exchange?

I'm a programmer, not a sys-admin, but my customer's sys-admins are not being helpful and after much googling I still can't find the answer to this. My Java application gets the following response ...
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1answer
6k views

Load balancing SMTP in a way that doesn't hide the source IP address

I need to load balance SMTP to handle some applications that don't know how to use MX records. I set up a Netscaler using the TCP option on port 25 and now Exchange sees the source IP as that of the ...
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1answer
17k views

New mail server can't send emails, only receives

I'm setting up a new mail server for my company with Ubuntu Server 11.04 and postfix/dovecot. I'm new on this so I have some problems. I'm getting it works only for receving mails from any address ...
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2answers
7k views

CBL This IP address is HELO'ing as “localhost.localdomain”

I am pretty lost here, my server somehow got into a blacklist. And I don't know why and how to solve it. Please take a look at the link below. CBL List - click here Anyone knows what is going on ...
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9answers
18k views

Emails are being rejected by some email providers

I have this asp.net application that sends out emails. The SMTP server is iis6. The emails are being sent on behalf of our application users and they have different domain names. Most of the email ...
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1answer
13k views

Yahoo Domain Keys setup, getting dkim=permerror (no key)

I'm working on getting DKIM installed on my outgoing mail server, to help my email deliverability to my Yahoo clients (all legit emails, etc, no spamming). I've got DKIM-Signature: and DomainKey-...
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1answer
96 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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3answers
2k views

How to limit amount of email sent by postfix to certain domains and control it by using mail header?

Goal I'm looking for a solution to limit rate of e-mails sent to specific e-mail operator (several Top-Level domains, all of them I know) on hourly basis. I also need some way to control the rate on ...
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1answer
2k views

Postfix multiple checks

I want to achieve the following with Postfix: Run all emails through a black list Allow any clients sending to a list of domains Allow some clients sending to any domain This is what I have: (...
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1answer
4k views

Postfix client host rejected

I set up Postfix+Courier+Roundcube on Ubuntu 12.04, but when I try to send an email with Roundcube, I receive the following error: /var/log/mail.log : Dec 30 20:54:35 server postfix/smtpd[31465]: ...
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3answers
1k views

Security Risk involved in disabling SMTP authentication on POP3 Server?

I provide IT Services to a client who, for the longest time in the world, has been using a POP3 server from Network Solutions to handle their email. At this time, I'm introducing the McAfee SaaS ...
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2answers
735 views

Creating a “fake” open relay to capture non-relayable outgoing mail with postfix

We occasionally have customer-provided servers in our technical support and engineering departments. They're isolated on their own VLAN, with strict firewall rules in place to minimize possible bad ...
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4answers
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How to determine if my mail server is configured correctly?

Does anyone know of an online service (similar to the ones that tell you if a site is up or down) that can connect to a specified mail server and perform checks to see if it is configured correctly? ...
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1answer
5k views

IIS6 SMTP and TLS on outbound connections

In the options for setting up the SMTP server hosted in IIS, there exists an option to enable TLS on outbound connections which I want. However I also want it to be able to fallback to clear text in ...
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1answer
122 views

Is reverse DNS a good method for promoting grey IPs from trusted domains to white?

I'm trying to set up a mail server using OpenBSD, OpenSMTPD, spamd, and pf. The first problem I've encountered is that many large webmail providers - like Gmail - will retry delivery from a different ...
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1answer
2k views

how do I set up two smtp ports for postfix?

A CentOS 7 server with postfix, dovecot, and mailx needs to accommodate mail being sent through port 465 and received through port 25. What specific syntax and files need to be changed in order to ...
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1answer
801 views

What PID is making outbound connections on port 25?

What is the most ready way to log the PID and process name of anything making an outbound connection on port 25? This is on a 2008 x32 server without the windows firewall enabled. I'm ...
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2answers
5k views

Sent items via Exchange SMTP stored in the users mailbox

Using Exchange 2010 server, is there a way to store outgoing emails in the mailbox's sent items folder when an SMTP authenticated user is sending an email via the exchange server's SMTP server? (I.e ...
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1answer
378 views

Does DKIM works with subdomains?

ISP's recommend you segment your marketing and transactional emails by using different IPs. I want to start using DKIM, but since DKIM is a domain based reputation system I wonder if signing with the ...
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2answers
3k views

Using DHCP to push SMTP server addresses to clients

I noticed on the Windows DHCP service there's an option to add SMTP servers to the information provided to DHCP clients. I've never heard of this before, but it sounds useful, especially for when our ...
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6answers
1k views

How to legitimately work around ISP rate limits

A lot of ISP rate limit the amount of e-mails that is sent from a particular IP address. What is the proper way to get around that rate limit? Our company has an iPhone application that sends many e-...
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3answers
7k views

Trouble with IIS SMTP relaying to Gmail

I appreciate that similar questions have been asked about how to setup SMTP relaying with IIS's virtual SMTP server. However I'm still completely stumped on this problem. Here's the setup: IIS 6.0 ...
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2answers
5k views

Mac OS X Server (10.5) mail trapped in queue

We've got mail accumulating in our Leopard Server's queue and not sure exactly why. This machine has required little maintenance over the years so I'm hoping someone here spot the obvious and save us ...
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1answer
2k views

Configure Domino to use SMTP routing and hMailServer

I have been trying for a couple of days to set up a Domino 8.5 server. Basically, I want everything to be run inside a local network. Right now I can send email to other user in the Domino directory ...
4
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1answer
712 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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0answers
235 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. ...
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2answers
9k views

Postfix rejects all incoming mail (Client host rejected: Access denied)

I've setup a working postfix server except that all incoming mail is rejected. When I try to send mail via telnet: MAIL FROM: <tom@valid.domain.com> 250 2.1.0 Ok RCPT TO: <tom@mydomain.com&...
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2answers
6k views

How to read the “MS ForeFront” antispam report in email header?

I'm trying to diagnose why emails I'm sending out from my server's IIS SMTP Pickup Folder are getting bounced back occasionally. One tech from a receiving company who couldn't receive the emails said:...
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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 ...
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3answers
193 views

Exchange 2007 - One server set-up

I'm trying to set up Exchange 2007 with just one server (not the Transport + Hub configuration, just a Hub). I installed the server with the Hub Role, and it's not accepting SMTP. I changed SMTP so ...
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3answers
5k views

Email date is wrong/missing

In the typical email setup when an end user views the date of an email, is that supplied by the sending server or the receiving server? Every once in a while I'll get complaints that the date on an ...