Email Servers





Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

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We got a notification of a periodic email issue where the senders email gets rejected with the message below.  I'm not sufficiently experienced with this sort of thing to understand where the problem lies.  I'd appreciate it if someone could take a look and what, if anything, we can do to resolve it.

Thanks in advance
Delivery has failed to these recipients or groups:

Moreau, Jenifer
Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept email from certain senders, or another restriction may be preventing delivery.

The following organization rejected your message:

Diagnostic information for administrators:

Generating server: S15-MBX101.S15.local
 Remote Server returned '< #5.7.1 smtp;550 5.7.1 Rejected. Spam detected.>'

Original message headers:
Received: from S12-MBX11-11.S12.local ( by S15-MBX101.S15.local
 ( with Microsoft SMTP Server (version=TLS1_2,
 cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1415.2; Fri, 23
 Mar 2018 11:41:12 -0400
Received: from S12-MBX11-20.S12.local ( by S12-MBX11-11.S12.local
 ( with Microsoft SMTP Server (TLS) id 15.0.1365.1; Fri, 23 Mar
 2018 11:41:11 -0400
Received: from S12-MBX11-20.S12.local 

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I am in the process of finishing up my exchange migration move. I had a question about moving the Journal Rules, Rules, Retention Tags and Policies. Is there a command moves these or does automatically get embedded when you spin up a new exchange? I am moving from Exchange 2010 to 2016.
Why does a signature need to be hosted?

I have an image of my business card I configured as a signature image with Thunderbird.

I send out emails to my other email accounts, and the image shows up fine. So, what is the reason I need to host the image?

I guess if someone has images blocked, they will not see it. So in that case, would they need to click a URL in order to see the image?

If so, I imagine this enables the recipient to select which image to view versus viewing them all?

I am trying to understand the value of hosting my signature image.

Please let me know.

Is my customers PC infected, or did they guess his email password?:
I just got this spearfishing email from my customer:
I am his supplier. We both use Office 365. Looks to me like they guessed his password, but I am not certain:
He is Customer Lastname, his email adress is
I am Supplier  and my email adress is
Received: from ( by with HTTPS via
 MWHPR03CA0038.NAMPRD03.PROD.OUTLOOK.COM; Mon, 19 Mar 2018 17:10:19 +0000
Received: from ( by ( with Microsoft
 SMTP Server (version=TLS1_2,
 cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.588.14; Mon, 19
 Mar 2018 17:10:16 +0000
Received: from
 (2a01:111:f400:7e51::206) by
 (2603:10b6:803:29::12) with Microsoft SMTP Server (version=TLS1_2,
 cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.588.14 via Frontend
 Transport; Mon, 19 Mar 2018 17:10:16 +0000
Authentication-Results: spf=permerror (sender IP is;; dkim=pass (signature was
 verified);; dmarc=none
Received-SPF: PermError …
I am in a pickle and have a new approach (Plan B at the bottom)

I need to forward my domain to a partner's website, but I need emails to work using my domain.

I prefer hosting at

The problem I had when creating a CNAME record was I got the domain to forward, but that broke the email. The MX records were being read from the target website, which is not RackSpace.

So, I canceled my email accounts at RackSpace and create new accounts at Zoho, thinking this would solve the problem.

It did not.

Here are my three attempts from BlueHost:

With A Record
With No A Record and No CNAME
With A Record and CNAME
Any other ideas for this before going to Plan B?

My new approach is to point my domain at a real super-simple website. In the index.html I re-route to the target domain.

Any problems with this?

My partner’s IT guy said it was okay to forward all traffic.

What does the index.htm look like?
What is that one line of code?

We're on Exchange 2010, and some of our Outlook 2010 users are getting this error below, when sometimes sending to ONLY ONE recipeint:

[Postmaster] Email Delivery Failure

This is a delivery failure notification message indicating that an email you addressed to email address :
[replaced email address for privacy]   could not be delivered. The problem appears to be :
-- Bounce - Recipient server condition

Additional information follows :
-- Too many invalid recipients

This condition occurred after 1 attempt(s) to deliver over a period of 0 hour(s).
We have a Throttling Policy in Exchange 2010 that sets the RecipientRateLimit to 1000.  We have a user that got a virus and was sending tons of emails.  Well he hit the rate limit and now is unable to send email for 24 hours.  

Now that we've cleaned up his device and changed his password, is there a way to reset the RecipientRateLimit count for this individual?

Dear Experts, I have one AD (server2012R2) and one Mail Exchange 2016 server. When I configured the complexity of password in AD and applied it with "gpupdate /force", the policy could not applied in Exchange mail users. They can still change the password with simple phrases. For example: no need special characters, or number,...

Can you please explain and suggest?

Many thanks!
I have 2 sql servers,  old and new.  They are external servers, not on my LAN, but there's an always on VPN, so they behave like they are on my LAN.
 With my old server, I can use the feature "database mail" to send a test email.
On my new server, that doesn't work, and I even am using the exact same configuration.

Any ideas why?  Is there a way to check the detailed logs, as I don't think sql is sending the emails.

1. checked the msdb database, table sysmail_log, and nothing there with errors, no entries there.
2. I checked my corporporate firewall and it's configured correctly as far as I can tell.
3. I checked my exchange server (hosted internally), and it's configured to allow my external sql servers to send emails.
4. I checked and did a test from the server and that worked fine.  

What else can I try to get the "database mail" feature to work, as I need my sql to start ending emails.
CNAME Record caused my emails to fail.

I hosted 2 emails at RackSpace for my domain, and verified they worked fine. This required me to update the MX records where I host my domain.


Then, before I could create a website, I was allowed by my partner to point my domain at his website.

The redirect worked once I created a CNAME record. brings up the site at

But the emails stopped working.

The error is "553 Relaying disallowed"

I called RackSpace and they said it's because the MX records at the, where points at, are pointing to Zoho (a major email provider).

So, my question is...

If I move my two emails from RackSpace to Zoho, can I have a solution where

1) domain forwarding is working ( brings up the site at
2) emails work as well (both ( emails work again)



Or, is there another way to configure this?

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We are using an Exchange Server 2010.  I have created a transport rule that inspects the subject field from users outside the organization for words like Invoice, Receipt, Statement, etc.  I have the email redirected to an account for spam.  In the exception area, the rule inspects the From address for email addresses or domains of allowed senders.

The rule has run out of space and I cannot add more addresses/domains.  There must be a better way.  I need some direction.
I need to add a reverse dns record in my dns configuration.

I am getting this error is the ip of the mail server

Remote host said: 451 4.1.8 Possibly forged hostname for

I have access to the dns zone  of the domain

Any ideas
Please provide me with the steps on how to export Outlook 2016 contacts into an online Gmail account.
When you type in in a web browser, theres all the work of resolving the name into an ip address and then your packets are sent from your computer to the EE web server and vice versa, going through routers around the web, right?

Contrast that with an email?  I was explaining to someone that large attachments in an email might cause the email to not be delivered as it routes its way through the web. Then I wondered... is the email actually going through  mail servers on the web and being reforwarded? Or just routers (on the backbone?). If it's just routers, do they actually care how big the total email is? It's just a lot of packets being sent in the same direction.

ie - is there really a limit to an attachment size limit in email OTHER THAN at the sender or receiver email server?  Yes, the sender server or receiving server can set limits to the size of the attachment.  But after resolving the MX record and sending to the receiving server.... what could get in the way?

I need to change the User ID that is being used to login to Office 365.  We have an on site Exchange 2010 server and have migrated to Office 365.  Our current domain and email address is and Microsoft created us a domain called  My users really have two email addresses, and  This is fine and we are using AD synchronization which is working fine.  

However, it makes my users log into their accounts with the account when accessing email or 365 in the cloud.  But at work in our domain, they are accustomed to using  Is their a way I can make it allow them to login with the other account id instead of the one Microsoft created?

Every time we move a mailbox from Exchange 2010 to Exchange 2016 we need to restart the Autodiscover and Exchange Web Services Application pools.

We are running Exchange 2016 CU6.  Does anyone know if a fix for this has been released yet?
Hello Experts,

We have exchange 2016 with DAG in our network.
One of our user is getting undeliverable email reports about emails that he didn't send and he receiving 100s of emails in a day.

Appreciating any advise and suggestions
Hello all, could you please provide some guidance on common best practices for configuring secure email relay?  What port number should be used, TLS, certificates, authentication, etc.  Thanks.
Hi All,

We have a hybrid setup with exchange 2016 and Exchange 2013 as we migrate. Were having an issue with relay from our internal scanners. They are able to send email internally but not externally. We have dns pointing to the 2016 server and we see the IP's in both Relay connectors on 2013 and 2016 email servers. However it wont send external from scanners, the error is invalid recipient on the scanner. However if we change the scanner to point to the 2013 server it works.  Anyone come across this situation or have any thoughts. Thanks Much
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I feel embarrassed to have to admit I know little about Exchange and the issue I am having here.

On an SBS 2011 standard box, years ago they set up a smart host send connector to go through a company that checks for spam filtering.

Worked fine for years.  Now the filtering company is saying there's loads of spam going out from our network through them (coming from different people in the company). They said they disabled the address till we can clean things up.  They said they felt a machine got infected. Wouldn't that machine send out typically under the user that's logged into that machine? not several different people?

Looking at the message queues in exchange management console, I see a smarthostconnectordelivery entry. there's (only) 27 emails there waiting to go out.  I can view the to / from for each. But the sender isn't available to be able to ask if they sent the emails intentionally.

a) is there a way when logged in as the admin to see the text of the emails to know if they are legit emails?
b) if a machine was sending out spam, wouldn't there be more than 27 emails waiting to go after 4 hours since they disabled that email address?
c) I am envisioning seeing the LAN IP that the emails were sent from to the exchange server, then I can see if these are all coming from 1 machine / check that machine for malware.

For mail that already went out, is there a way to see the contents of those emails?  The spam filtering people sent me…
My boss has a new iPhone8. I've set him up to access the IMAP server at the office. Inbox works just fine and he can send messages. The problem is that the Sent and Trash folder on the iPhone do no synchronize with the server. Apparently, this is not an uncommon problem since I've found lots of posts about it. However, none of the instructions I've found so far seem to work. How do I do this?

The mail server is Dovecot IMAP. The iPhone is using the normal mail facility, nothing special or 3rd party. The selected server setup is 'Other'. Inbox synchronization works. Messages deleted on the iPhone, and sent messages are not synchronized with the corresponding folders on the IMAP server.
I have local exchange 2013 CU18 servers set up as a SMTP server.  I have set up a send connector to go to a smart host.  This works fine.  But I need to make sure emails coming from other systems inside of the domain are using an authoritative domain to send email via my SMTP servers.  I know I can set up another send connector using MX records, but I have to have all emails go out my smart host.  

im trying to create a new Exchange 2016 server to migrate from 2010. However during the setup im getting a message saying that there is a 2000 or 2003 exchange server on the network.

We have never had a exchange 200 or 2003 server. The first on premise excahnge server was 2010 as part of SBS 2011.

I cannot find any references to an older exchange server.

Any ideas how i can fix this.
Our client often gets complaint's from their customers not being able to send attachments through to them because they continuously get rejected for being too large.

They're using an on-prem 2010 Exchange server.  
The initial message size limit send/receive was set to 30MB.
Their hosted anti-spam solution, Trend micro, has a limit set for 50MB.
I changed the on-prem 2010 Exchange server send/receive to a limit of 50MB for troubleshooting purposes.

We still get bounce backs when sending anything typically over the size limit of 15MB. The message comes back indicating it exceeds the limit of 20MB.  After checking all the settings (that I know of), I don't know where the size limit of 20MB is being set.  I know that messages grow in size beyond the initial attachment limit, but not to this degree.

Is there anything specifically I've missed in checking?

Thank you!
Hi Guys,

We having issues receiving mail in Exchange 2016.  

We use a smart host to deliver mail to our Exchange 2016 server via port 25.  
By means of the "Default Frontend" receive connector in Exchange.
Basic authentication is enabled, as well as Anonymous Users permissions group.
Scoping is the local IP of the smart host.

Mail is piling up in the smart host queue.
Receiving mail was working fine up to a recent power failure.

During troubleshooting, I found no authentication username & password configured in the smarthost.

Can a receive connector in Exchange receive mail from a smarthost via SMTP without authentication?
The smart host logs does not show any specific error related to Exchange not receiving the mails.

Using an Exchange mailbox to authenticate, should I use the format user@domain.local as the username to authenticate?

Email Servers





Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

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