Email Protocols





Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

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Hello everybody,

i'am trying since a few days now to get my new exchange server to work.
the main problem is the incapacity to receive emails from outside, Inside the domain is no problem.
also sending emails internal and to external domains is no problem. OWA is working properly too.

impossible to configure Outlook with the exchange server, fot imap its reffusing the authentification and saying ActiveSync isn't active (but it is)

i get no error message when the emails didnt get received, also no error message while sending them from outside.

ports on firewall/router are open, DNS server is working properly.

if anyone has any idea to resolve this or if somebody needs remote access while iam avalaible, i can do that.

Best regards
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Dear Experts, we are using Exchange 2016 on-premise, the problem is when users send emails to incorrect addresses, the postmaster showed the error (in details) in MS Outlook but OWA.

The emails are synchronized from OWA to MS Outlook, but there is no content in postmater's email on OWA. Could you please suggest?
We are having a strange issue with Outlook 2016 on  Win10 domain joined computer.  The issue is when trying to create a new profile Outlook will crash when "searching for setting".  It seems like its having an issue with autodiscovery but, I  can set that same user up on another machine with out an issue.  We also notice that when it crashes the our on-prem Exchange server shows to "Bad Password Counts" against it.  The users account has not been changed in several months and if we put outlook 2013 on the 10 machine it works fine.  I have a ticket with Microsoft but, they are not helping much, they are asking me to do the same stuff I have found online doing my own research.  I am just wondering if anybody else has seen this.  

When testing connectivity everything seems fine but the issue seems to be between the client and Exchange.  We have one Exchange server and its on prem we don't have any cloud based hosting for email.

Any help or other troubleshooting tips would be helpful.

Dear Experts, can you please suggest us 2 problems:

1. How can we reset multiple Gmail accounts at the same time? (We are using Gsuite, and are Admin accounts)

2. How can we configure multiple MS Outlook accounts at the same time on Window OS?

Many thanks!
When a user function or operation executes in our application, a confirmation email is sent out, using the SMTP credentials found in the web.config file.
Q- When an external user has logged onto the application, and is performing the process, could their internal corporate firewall block the email being sent out by the app? I am not sure if the email is generated from the host server, or via the user's local session.
Thanks for your input.
I've encouraged the user to contact Centurylink on this.  But maybe someone has another idea.

The user uses Centurylink Webmail.

When Composing or Replying, the names can be typed into the form.
But the Body cannot be typed into or Pasted into - at all.
Google Chrome shows a blank body that doesn't respond to a mouse click into it.
Internet Explorer shows "this page can't be opened" and mouse clicks also do nothing.

So, the user cannot send emails at all.

And, I can duplicate this on my own computer - which is entirely separate except for the email account login.

I'm writing some custom code to analyze spam for incoming mail to our mail server.  I need to know what the following encoding method is from the text snippet below.  Have tried several things (UTF-8, MIME, etc) and haven't had any success so far:

Subject: =?UTF-8?B?8J+OgSBCbGFjayBGcmlkYXkgaXMgT04u?=


i am posing on behalf of a friend whose gmail was hacked and now the hacker is posing as my friend and trying to carry on his business activities.   How does one stop the hacker, and how does one take the remedy with google.  Are there any steps to follow.  Thank u. Regardss
Is there a way for pop3 or imap account to sync calendar with gmail as alternative?
Or to import the pop3 or imap calendar to gmail account?
We are providing antispam service to few clients using our builtin antispam in our server.
Now customers requesting for interface to release the quarantined emails.

Is there any antispam software you guys know which can provide interface and filter spams?

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Dear guys, we have an Exchange 2016 on-premise server and would like to increase the attachment's size of users' emails to 100 MB. We did some research and followed but still got the error "The following files weren't attached because adding them would cause the message to exceed the maximum size limit of 25 MB: smex_12.0_ag.pdf. " when attached a file that is bigger than 25 MB into an email. Could you please suggest?

Attached pictures are our settings, we restarted IIS, Transport services, even server itself but did not help!
I'm currently using a Gmail account for Veeam email notifications using the server addresses shown in the first screenshot and am successfully receiving Veeam email notifications.

However when I try to use the exact same Gmail email address and email server settings for Server 2016 WSUS email notifications (in the second and third screenshots) these email server address notifications don't work. I receive the error message shown in the last screenshot which says

"System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. i8sm33761833pgq.67 - gsmtp
   at Microsoft.UpdateServices.Internal.BaseApi.SoapExceptionProcessor.DeserializeAndThrow(SoapException soapException)
   at Microsoft.UpdateServices.Internal.DatabaseAccess.AdminDataAccessProxy.SendTestEmail(String emailLanguage, String smtpUserName, String senderEmailAddress, String smtpHostName, Int32 smtpPort, String recipients)
   at Microsoft.UpdateServices.Internal.BaseApi.EmailNotificationConfiguration.SendTestEmail()
   at Microsoft.UpdateServices.UI.SnapIn.Dialogs.EmailNotificationSettingsDialog.backgroundWorker_DoWork(Object sender, DoWorkEventArgs e)."

There is no where within the Server 2016 WSUS email notification settings to select to use secure connection (SSL/TLS).

So what is the correct Gmail email address server address setting to use to successfully send notification emails?
I have a customer that I inherited running Red Hat Linux ES 3 that wants to send email from the Linux side.  
I need to be able to send email using port 587.

cat /etc/redhat-release
Red Hat Enterprise Linux ES release 3 (Taroon)

The Windows support person says smtp must use port 587.

SMTP:  Port: 587

smtp            25/tcp          mail
smtp            25/udp          mail
submission      587/tcp         msa             # mail message submission
submission      587/udp         msa             # mail message submission

Since 587 is used by submission can smtp also be changed to 587 in the /etc/services file?

netstat -tanp | grep send | grep LISTEN
tcp        0      0  *    LISTEN      483/sendmail: acce

The Windows support person also says the following:
The Windows server is running DNS, so you may want to change the DNS servers to:
It should resolve "" to

cat /etc/resolv.conf
search appemc

cat /etc/sysconfig/networking/devices
# Intel Corp.|82540EM Gigabit Ethernet Controller

cat …
Dear Experts, we got an Exchange 2016 server and have an auto mail account, for example:

Dev Team is using this account to sent bulk emails to users via C# code but when they logged into this account in Exchange, there is no any item in Sent item folder. Could you please suggest? Many thanks!
Is there an easy was to set up email (other than standard received notice) to determine if an email sent has been received. We keep having issues with our emails not received.
When I print a Gmail Inbox email, it's teeny-tiny, like 65% to scale, barely readable when it prints. I set it to 100% Scale, but nothing happened when I changed that (it starts at 62), here:
Inbox prints small
But when I print from regular Gmail, it's normal, here:
Gmail prints ok
The difference seems to be Inbox / Gmail, so ???
We have apps that send alerts out via SNMP (think it's v2 SNMP): is there any way these
events are sent to an SMTP server (we use Exchange) or to SolarWind (our monitoring tool)?
If sent to SolarWind, we want to be alerted via email or SMS.

Our apps read the events from a custom Oracle DB (from a SWIFT application).

We have Splunk SIEM being deployed but not ready yet so wanted to use the other 2 options 1st.
One of our company entities is currently using the hosted IMAP e-mailed provided for free as a part of their website hosting account.  I really want to move them to Office365, but the price difference - from "free" to $$$ - is making it a hard sell.  The companies has a group of employees - 30-40 - that really can get by with the IMAP hosting.  Another smaller group of 10 or so employees would really benefit from the features of Office365 hosted e-mail.  My thought is keep email to pointing to the IMAP server via its MX record.  Setup Office365 to a subdomain and have its own MX record setup.  This seems possible, but I don't exactly know how Office365 setup will go in a subdomain.  Also, If I setup Office365 in this subdomain environment, would it be possible to move it to if we ever reached a point where we were OK with paying for O365 subscriptions for all of the users?
Hello, does anyone know to prevent local users from authenticating over an SMTP connection and spoofing?
This is mainly an issue when spammers compromise an account to send SPAM.
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I need to put a function on my emails where we can track the initial link that is being clicked.  The way I currently do this is to put a small php/asp script onto the website and add the script onto the hyperlink - something like this:

When the script runs, it takes the user to the relevant page (PID) and sends an email with the ID number to a designated email address (that can then be processed). This function is going to be used by several companies, so I need to minimise what I ask them to do when setting things up.  

Historically the companies that have used an early version of this function have been fine with adding a small php/asp script to their site and setting up a mailbox.

Ultimately, the marketing guys just need the ID, whereas the Tech guys need to be happy (security, ease of implementation etc.). So, is this a good way to do it - or is there a better method?  

A user who used to be an Office 365 global administrator receives "Identity synchronization Error Report" emails. She continues to receive these emails even though her global administrator role was removed a month ago. Now she is just a standard Office 365 user without any administrator roles.

Also even though I am an Office 365 global administrator I don't receive these email notifications nor do other Office 365 global administrators within our organization.

Where within Office 365 do I need to go to edit who receives these and other Office 365 error message and notification emails?

Office 365 sync errors email
We have a legacy software that does not support TLS so we relay the emails via an IIS relay that authenticates and send out via Office 365.

Emails to certain recipients are bouncing with the NDR 550 5.6.11 SMTPSEND.BareLinefeedsAreIllegal

This has just started recently about 2 months ago .

This Microsoft links explains why -

 What's a bare line feed in email messages?

Usually each line of characters in an email message ends with a carriage return followed by a line feed (CR LF). A bare line feed is a line feed (LF) character that is not immediately preceded by a carriage return (CR) character. In other words, instead of a line ending with CR LF, it ends with only LF.
This worked fine before, why did it stop working recently?

Until recently, Office 365 automatically removed bare line feed characters from mail to help it get delivered to recipients using older email servers that don’t support chunking and the BDAT command. The support for BDAT is required by the email industry standards referenced in RFC 1830. In an effort to better support security standards, like DomainKeys Identified Mail (DKIM), Office 365 no longer removes bare line feeds from messages. As a result, messages sent to users with older mail servers may be more likely to be rejected.

Their suggestion is to make changes on the recipients server which is not possible so what can I do on our end to fix this?
When a user within our organization sends a certain Power Point file as an email file attachment using Outlook 2016 the email arrives in the recipients Inbox but the Power Point file attachment is no longer attached to the email.

We believe this is happening because Office 365 detects malware or some other type of problem with this Power Point file attachment. This file attachment is well within the file size attachment quota limits.

The sender doesn't receive any type of notification saying that the file attachment has been dropped or quarantined and the persons receiving this email don't know that the email was supposed to have a file attachment.

What can be done to change this so that if Office 365 ever drops a sender's file attachment the sender will receive an email notification that the file has been dropped or quarantined?

Is it also possible to make it so that the persons receiving this email will also be notified that the email they have received has had the file attachment dropped or quarantined?
What does the NDR code 550 5.7.360 mean?

A user received an NDR with this code in the email NDR which said that the email couldn't be delivered.
We have recently migrated from an internally hosted Exchange 2010 to offie 365 for education.

Currently our exchange is still present, but only for the purpose of SMTP relaying from our applications. I believe this is causing problems because of our SPF record.

I would like to know is it better (or even possible with the free/educaiton licensing.) to use office 365 for relaying. or should i just adjust my SPF records and continue to use the internal relay.

If the answer is adjust SPF record. can i please get some guidance on the exact syntax ?

currently it is setup as: v=spf1 -all

Would i add another record, or add to the existing one ?

Thank you,

Email Protocols





Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.