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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Windows Server 2012 R2 - SMTP Relay - Connection Dropped by Remote Host

We setup a relay server for Office 365 on a Windows Server 2012 R2 instance roughly a year ago. Everything has been fine until the past week when the relay appears to lock up and e-mails continue to ...
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2answers
40 views

How do I send (legitimate) email on a dedicated server as appearing from different domains?

We need to send email using PHP's mail() function (Actually CakePHP, which wraps that function) directly from our dedicated server (app.ourserver.com). We would like to send mail from ...
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1answer
38 views

SMTP network ACL on AWS

I have a very restricted ACL for my VPC. We have a public subnet and a private subnet, each subnet has its own individual ACL. What I don't understand is why the following ACL works for sending email ...
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78 views

Exchange 2010: not receiving NDR when sending email using SMTP to none existing external mailbox

We are sending email using smtp port 25 in a local Exchange 2010 server We do not set username nor passwords in the SMTP connection, only "form" address. Mails are sent to external recipients after ...
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0answers
32 views

Postfix smtp relay to Office 365 for certain sender-domains

I'm running Debian Wheezy with Postfix 2.9.6 and I'm trying to enable the smtp relay for some certain sender-domains for office 365. I whitelisted my IPv4 for smtp relaying on the exchange server: ...
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1answer
37 views

Use two different mail servers for a single domain [closed]

sorry for my english, I have used Google Translate. I have a Arsys host (an ISP host from Spain), which gives me 50 email accounts with 6GB of storage each. I have about 6 accounts of those who need ...
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2answers
45 views

Postfix admin/Postfix: Send e-mail from an alias

I use postfix (basically postfix admin) to define my e-mail inboxes and SMPTs. Say I have a one e-mail inbox: maininbox@mydomain.com Now I have a few aliases. Say I have the alias: ...
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1answer
37 views

503 AUTH command used when not advertised exim4 - Outlook

I do keep on getting this error: 503 AUTH command used when not advertised I have seen this question : exim configuration: 503 AUTH command used when not advertised The difference is that i do not ...
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0answers
11 views

Cannot connect to smtp mail server [duplicate]

I have an installation of Postfix & Dovecot on a Centos 7 server. While being logged into the server via ssh I am able to use telnet and openssl to connect to localhost like openssl s_client ...
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44 views

Configure Postfix to send emails from my domain name

All my clients use gmail, but would like to use the domain name that I own, say domain.com to send from. I've already figured out how to forward emails that go to domain.com to its respective gmail ...
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1answer
77 views

Telnet: Unable to connect to remote host

Related Threads: SMTP server works, but telnet to port 25 does not Can't connect to SMTP server The problem I have a server running Debian 3.2.65-1 and i am having some problems to connect other ...
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1answer
139 views

reverse proxy for multiple SMTP / IMAP servers

Instead of giving our clients server name's like beta.example.com as IMAP / SMTP servers, we'd like to use smtp.example.com. We have a database of all domains / e-mail servers and corresponding mail ...
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1answer
35 views

STARTTLS sendmail handshake failures on SMTP and retries

I'd like to gracefully handle sendmail STARTTLS handshake failures. On outgoing mail, it would be best if there were an immediate retry without STARTTLS in the case of failure. On inbound mail, ...
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0answers
30 views

Postfix STARTTSL works in LAN but not from external (centos 7)

if I connect in LAN on port 25 to my mailserver 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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88 views

How to send an email with Powershell that doesn't end up in spam folder to Gmail?

I have various PowerShell scripts on Windows Server 2012 R2 that I like to notify me via email upon completion, so I setup a local SMTP server that is restricted to 127.0.0.1 only, and use this ...
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0answers
10 views

Firewalld not opening port 25? [duplicate]

Lookst like firewalld is not opening port 25. I tried adding the smtp service, and port 25 separately as well, yet, I am unable to telnet to the server. Any tips? [root@host ~]# firewall-cmd ...
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2answers
148 views

How can I reject spam before reaching SMTP on Postfix

My server has started receiving thousands of attempts to use my mail server to send spam from dynamic.hinet.net. The attempts are always rejected, but it's non-stop. I'd like to block these attempts ...
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0answers
40 views

Using MX records for load balancing on *outgoing* email: bad practice?

I operate a Rails application (a Discourse forum) that needs to send out email. My sysadmin told me I shouldn't use a specific outgoing mailserver, but rather specify my domain and have my app lookup ...
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2answers
65 views

Can Mandrill route inbound email to webmail (like roundcube)

My main issue is I setup a small server, and my ISP blocks port 25. I've setup Mandrill as a relayhost on port 587 in postfix, so that solves my sending issue. I know Mandrill can be used to route ...
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1answer
52 views

SPF check failed

I am having trouble with failing to deliver mails with my setup. Server 1 - example.com + Direct Admin IP: 111.111.111.111, default domain (provided by hosting company: vps11111.company.com Server 2 ...
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1answer
59 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 ...
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1answer
35 views

Add a second IP to SPF record, from an external SMTP server [closed]

I would like to add the IP of an external SMTP server to an existing SPF record, which is looks like this: "v=spf1 a mx ip4:185.6.139.6 a:frey.mailpool.1.netmask.hu a:frey.mailpool.2.netmask.hu ...
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1answer
23 views

Exchange from field in iso format when ø character in name

I have setup a forward connector on Exchange (2010 SP2) named (f.e.) target.domain.no. The forward record points to a Windows Server SMTP Server (EMSERVER). Now I see in that emails that have the ø ...
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131 views

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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2answers
130 views

Can send email but can not receive email on Windows Server 2012 R2 with MailEnable

I am configuring a VPS on Windows Server 2012 R2 using MailEnable as email server. As the port 25 is blocked by ISP so I use port 587 instead. When configuring on email client Outlook or ...
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1answer
169 views

Sendmail: “TLS verify=FAIL”, “554 5.1.8 : Sender address rejected: MX record not found”

Have been struggling for a day already and can't find solution. When try to send mails to some hosts: Jan 5 10:31:37 vps**** sm-mta[2192]: STARTTLS=client, relay=mail-x.*****.co.uk., ...
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1answer
36 views

SMTP Server with dynamic / Static IP

I have 3 servers and 3 IP's. Server 1 - Static IP - 111.111.111.111 Server 2 - Static IP - 222.222.222.222 Server 3 - Dynamic IP - 333.333.333.333 Now Server 3 is always assigned the IP ...
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142 views

cant send to gmail. Remote host said: 421 4.7.0 Senders Guidelines

I have a SMTP account by hostgator. It has been working OK for a few years. in the last week all emails sent to gmail accounts are bounced with the following message: Could not deliver message to ...
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1answer
277 views

Postfix “Connection timed out”

I try to send a few emails, but postfix send only 3 emails every 10-20 min. After that postfix sends 3 emails, I get the error: "Connection timed out". mail.log: Jan 4 12:16:39 mail ...
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88 views

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 ...
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32 views

Incoming SMTP to Azure Windows VM going to C:\inetpub\mailroot\Queue\ instead of Drop\

I have an ASP.NET web app that needs to process incoming SMTP email from any Internet user. I configured IIS and my Azure Windows server 2012 R2 VM end point, but when I send email from the Internet, ...
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0answers
101 views

Trying to set up Gmail “send mail as” SMTP mail function

Alright, so I've come here as a last resort hoping to find that last bit of help I need to solve this. I've spent the last two days scouring for answers without actually getting anything direct. First ...
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1answer
39 views

how to stop incoming SMTP .EML attack on an Azure Windows VM

This morning 1:53am, my Azure VM began receiving unexpected .EML files in C:\inetpub\mailroot\Queue. By about 6am when I first logged on, it had received over 36000 files. As a workaround, I stopped ...
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2answers
50 views

How to find out who is sending email

I have a server which doesn't have much activity. Today, suddenly server load went higher than 12 which compared to its normal value(0.5) is way too high. I checked and found out that postfix is being ...
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1answer
131 views

SMTP (postfix) and iPhone - can't send emails - reject: RCPT

I try to setup email server already 2 days, everything work flawless when i use roundcube on PC, I can send and receive emails, but problems start when I want to setup my email on iPhone. I can ...
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1answer
59 views

Postfix - Host or domain not found

I installed postfix on my centos. this is postconf -n output: alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases command_directory = /usr/sbin config_directory = /etc/postfix ...
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25 views

How to show email addresses in Outlook 2013 SMTP logs?

I need to troubleshoot some client-side issues while sending SMTP messages using Outlook 2013; I've turned on diagnostic logging, however the sender and recipient addresses are hidden in the logs: ...
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0answers
39 views

ICEwarp 11 mail server ERROR with relay mail

I have a promblem when i send mail from icewarp to relay server. user1@mydomain.com send a email to xyz@yahoo.com through mail.myrelay.com mydomain server and myrelay server in a DATA ROOM. I can not ...
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1answer
84 views

How to configure exim4 for both incoming SMTP for local delivery and relay for authenticated user

I want to use my exim4 mail server as local delivery for anonymous sender for my localdomains, and relay to everyone only for authenticated users. Is it possible?
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1answer
248 views

How SMTP (receiving emails) works?

I have a very hard time to understand how SMTP works. I've read already: Message Submission for Mail Internet Mail Architecture Internet Message Format Simple Mail Transfer Protocol I know the ...
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2answers
255 views

How to allow login to a SMTP server better than with password?

I'm planning on creating a mail server, but I don't want to use passwords at all. They seem a wrong security choice to me. I'd love to use a certificate to login. This seems easy to do in HTTP, but I ...
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1answer
138 views

OSSEC alerts without hosting SMTP

I've been searching without a solid solution yet. I need to send OSSEC email alerts from my OSSEC server, but without hosting an SMTP server (postfix, etc). I get rejected by the Google SMTP servers ...
10
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3answers
282 views

MX priority server behaviour

This is a question about MX procotol priority. If I have two server as MX with different priority: MX 10 serverA MX 20 serverB Is this guarantee by the protocol that the MX 10 is the prefered? Can ...
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1answer
32 views

Remote Postfix server for email relaying multiple domains

I have a local server at home that needs to send and receive email but my ISP blocks port 25 in and out. The local server is running Debian 8, has Virtualmin installed on top of it with postfix and it ...
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1answer
96 views

Postfix: Set custom SMTP Banner based on domain (same ip) used to access server

I have multiple domains on my server pointing to the same ip address. How can I setup postfix to greet with each individual smtp banner based on the domain name? I've searched everywhere but didn't ...
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95 views

DKIM fail signature doesnt verify

I had setup postfix and dkim and keep on getting dkim=fail on port25 and gmail checks. DKIM check details: Result: fail (signature doesn't verify) ID(s) verified: Canonicalized Headers: ...
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1answer
35 views

SMTP relay for multiple subdomains

here is my situation: I have a few subdomains: x1.example.com, x2.example.com.. IP adresses for these subdomains in local network : 192.168.1.1, 192.168.1.2.. They are not reachable from internet. I ...
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1answer
54 views

“lost connection after UNKNOWN” (OpenDKIM + postfix receiving emails)

I had a fully working mail server before installingopendkim with TLS with a free StartSSL certificate, that Thunderbird could interface with properly to send/receive email. My distro is Debian 8. ...
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0answers
21 views

Emails sent by my SMTP Service on Windows Server 2012 going to Spam folder [duplicate]

I'm trying to setup the SMTP Service on a Windows 2012 server (Amazon EC2). I followed this guide for configuring it, and I also added in Godaddy a CName record with the Host "mail" that points to ...
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1answer
55 views

No control panel equivalent of exim /etc/mailips file for configuring IPs for each domain's outgoing mail?

I have a problem with outgoing SMTP mail being sent with the wrong IP address. I use exim for outgoing mail. I found a guide "How to manually configure Exim's outgoing IP addresses", which suggests ...