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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I have a client using IMAP in Outlook. Yesterday she wasn't receiving any emails. I looked at the account settings, and they were all correct. I tested the connection, and the test message went through just fine. Then I closed the windows. After a second or two, her emails started coming in. This morning, she again was receiving no emails. I checked the settings again and again tested the connection, then closed the window. Again, after a moment or two she started receiving emails. She never has a problems receiving emails on her phone (also IMAP). It's like every day I have to remind Outlook it can find the server by testing the connection. This is very inconvenient. What can I do?
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Hi All
I need some help please.
I have 5 Exchange 2010 SP3 RU 21 servers running on Windows 2008 R2.
On 2 of my servers mail all of a sudden stops flowing to them.
There’s enough free space across all drives.
The servers are virtualized running on top of Hyper-V Server 2012.
Certificates are valid.
Server time is correct.
When I attempt to restart the transport service on the affected server it fails to stop and then you can’t start it again.
Even going via task manager and ended the exe relating to the transport service doesn’t seem to help.
The only thing that restores mail to and from this server is a reboot.
Any ideas?
I can send out message via Telnet fine like
29y.pngbut why I encounter problem in outlook below
30c.pngWhy? What other Email client can be used instead of Outlook?
Dear Experts, we have Exchange server 2016 on Server 2012R2. Can we using Exchange Management Shell to forward emails from a user's mailbox to another's ?

How can we do it? Many thanks!

For example:'s inbox have some emails from, we got a request to forward all emails from in user1's mailbox to
Comcast (Xfinity) is recommending that users move to IMAP for email & I am wondering if there are any downsides to this.
My initial concern is that there will be a ton of duplicates in mailbox at the start, or is that not so?
From what I gather, they have a 10 GB mailbox limit - when it gets near full, would I be able to archive mail to a pst (or any other option)?
Would it be best to start with a new profile?
What about getting everything currently in my pst file into the IMAP folder - would I just open pst file & copy into IMAP folders?
What about phones, ipads, etc - how long till all of that synchs up?
About to do this for a neurotic friend & want to be prepared...

I have an Exchange 2010 server Version 14.03.0399.000 which I believe puts it at Service Pack 3 rollup 21. I just did the rollup last week. This server has been running for years flawlessly until I ran this last rollup. Now for some reason, about 3 times a day the SMTP protocol just stops answering.

I believe I’ve got it narrowed down to something happening with the Microsoft Exchange Transport service. Before SMTP stops working I can restart this service, but after SMTP stops talking I can’t restart it, it just hangs.

If I perform a reboot on the mail server all is fine again for 6 to 8 hours.

Any help would be great
HI Folks,

I wonder are there any experts out there that know how to analyse email header source. One of our clients received a bogus email that appeared to come from one of our staff members email address.. it did not. .. unless his email account was compromised.

I've asked the receive to send me the header of that bad email and they did. I put the message header into a Google Product called "Message Header Analyzer" and the results are attached.

My question: from this is there any way to determine the source of the email? Our domain is So did the come directly from us or is it from another source and just looks like from

Am I making sense here? Any help would sure be appreciated!

An organization I support needs to have a local Exchange 2016 server setup that will integrate with Office 365.

Please provide me with step-by-step instructions on how to do this.
Good afternoon everyone!

I am performing mailbox migrations in a Hybrid environment!

Why am I having a problem in 3 boxes where I do not change 2013 are they? Archive while performing sync is giving the following error.

This Mailbox has 16GB, but this is being used as a mailbox or several users as members.

Migrated data:
Migration rate:
Error: MigrationPermanentException: The file size 104.8 GB (112,571,089,611 bytes) exceeds the destination quota of 100 GB (107,374,182,400 bytes). The file size 104.8 GB (112,571,089,611 bytes) exceeds the target quota 100 GB (107,374,182,400 bytes).
I'm configuring postifx mail server in centos 7. i have facing problem related rate limit outgoing mails. my requirement is 3 mail every 1m. so what type of configuration in and i hope you will help me.

Thank you
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I have a website on an internal domain. It's hosted on IIS and uses some javascript scripts and SKEL for for content generation, resizing, it works well as a responsive web page.
There is a form to send email, it is centered around using an external email provider. I have set it up so that it puts the requested data, (type of info requested, name, email, etc) and puts that where it belongs in the users own default email client. (generally Outlook). We have our own SMTP server.
My question is what is the simplest approach to get email sent using the form? The server is Windows server 2016, IIS. I have looked up stuff and see PHP, ASP it's kind of crazy how complicated it gets. Maybe I have not found the right tutorial.

I was trying to send emails through powershell on a computer PC01. and received error message blow
"InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpException"

I also tried to run the same script on another computer PC02 in the same subnet. it worked.

Both PCs can telnet to the smtp server on 25 successfully.

I have also tried to use ISP smtp to send email which was the same result PC01 didn't work with the same error. PC02 worked.
I checked the even log, no outstanding errors or warnings found.
I have also tried to turned off firewall and antivirus program without luck (which shouldn't be the issue as I can telnet to port 25 on the smtp server)
hostupon shared linux web server

for email

I do not see ALL my sent email unless I log into a browser

on devices (iphone/android/thunderbird) I tried imap and pop

Is this a fault of imap/pop
or is this using an inexpensive webserver
What are the steps on how to setup Open Relay within Office 365?
What are the best free services for sending emails without SMTP authentication?

I need to configure my organization's WSUS server for sending notification emails and would prefer to use a free account that doesn't require SMTP authentication.

What are the best free services for doing this?
What is it within certain Outlook 2016 autocomplete email address entries that can cause emails sent to that email address to bounce (even though the email address is correct)?
, on occasion we have seen malware delivered to a user’s inbox and we would like to be able to pull those messages out.

Is it possible to have a powershell command that could remove these e-mails based on items like the senders e-mail address and subject?

we have mailboxes in office 365 but we have proof point gateway through which incoming and outgoing emails go
An important user within my organization received NDRs while replying to emails sent by someone outside of our organization.

We are using Outlook 2016 and Office 365 as our email server.

However, later on the same day, someone else within our organization was able to reply to the exact same emails and these emails reached the person outside of our organization without any problems.

Neither person sending these emails had any attachments sent as part of these email replies.

Since the person we are emailing outside of our organization is a very important person we can't send any test emails or reply to any existing emails to simply test if this issue has been resolved.

So are there any ways we can simulate sending or replying to an email to this person outside of our organization to see if the original issue with the user within my organization had with sending emails to this outside user has been fixed?
i want to set up DMARC AND DKIM,

I have proof point and mailboxes in offic e365

where do i need to set up in external DNS or any steps defined.

i believe SPF is set up in external DNS
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Different employees at our company have had a problem with a large number of malicious outbound emails sent out from their company email address, causing our email service provider to shut off our service until we reset every account's password.  This has happened 5 times now.  When you look at one of the employee's Outlook programs, you don't see the malicious emails in the sent items, you only see the "bounce back" emails in the inbox, reporting that the email wasn't accepted by the recipient.  Neither McAfee nor Malwarebtyes detects malware on the employee's computer.  How can we figure out how these malicious emails are being sent out using the company's email addresses of our employees?  Could undetected malware be running on some of our computers that gives an outside person email passwords that he/she is using to send malicious emails from our accounts?  Is it more likely that our computers are sending out the malicious emails even though they aren't being logged in the sent items folders?  Could someone be intercepting our unencrypted emails and extracting the email password from them?   We have McAfee Orchestrator and a Fortigate 101E firewall appliance?  Could either of these things be used to troubleshoot the problem?

I created the 3 transport rules on the on-premise Exchange mentioned in this article:

These rules are not applying, in a test message I verified that the mentioned header
X-Forefront-Antispam-Report is populated:


The header contains "SFV:SPM" so the first rule should be applying... I checked the message tracking log for the test message but it just delivers...

I enabled pipeline tracing on the on-premise transport hubs but no rule tracking files are created (even though a different rule was applied).

Any ideas?
On a recently upgraded win 7 home to Win 10 home desktop PC, user uses AOL webmail.

says that from some users, when they expect an XLS or DOC /DOCX file(s), they ONLY get a file ending in WDL extension.  That's a text document that has the expected file name - kinda like a packing slip in a box.  But that's all that's attached. Not the expected file, just this packing slip text file with the WDL extension.

I told them to have the sender resend and include me.  But sender is a law firm / concerned with confidentiality (but yet, he's using an AOL address : )

So we set up a gmail account and the sender will send to both the aol and gmail accounts and we'll see if it's a sender issue.

I asked if the sender is a new employee (doesn't know how to send attachments?) - the user said no
Did the sender start using a new email system that includes a link to a secure website to get the attachment - the user said no
Are the files too large? Supposedly no.  There's a number after the file name, supposedly the file size?  in one email, it was 256.  (bytes?  KB?)

Any thoughts on why someone would get a WDL file rather than the actual file?  Yes, there's loads of ways to approach this / try troubleshooting. But getting the sender to send emails / answer questions about what they are using to send, etc. is hard.  so trying to figure things out with limited info.

googling, it doesn;'t come up with anything about attachments / emails.  WDL is some gaming file extension …
Is there a way to limit registration to certain email domains?

//email validation / only allow certain domains to register
      $allowed_domains = array("", "", "");
    $email_domain = array_pop(explode("@", $email));
   if(!in_array($email_domain, $allowed_domains)) {
    //Not an authorized email

this code isn't working, it allows all email addresses to register.

You can use IMAP or POP3 protocol to configure your Gmail account in MS Outlook. However, after using IMAP account in Outlook for some time, many users want to change their mail settings from IMAP to POP. Today we will discuss how quickly you can change your IMAP configuration to POP3.

What is IMAP?

IMAP stands for Internet Messages Access Protocol. In an IMAP configuration, the email client keeps a copy of the mailbox on the local system without deleting it from the email server. The advantage in this case is that you can access your complete mailbox data through various devices (of course with proper IMAP configuration).

Advantages of IMAP

  • Quick and easy access to emails from different geographical locations.

  • In IMAP, any items deleted from the user system is still available on the server.

What is POP3?

POP3 is an abbreviation of Post Office Protocol version 3.  When your email application is configured with POP, then all your emails are downloaded to your email application. Then emails can (and should) be permanently deleted from the mail server.

Advantages of POP3

  • Your emails are stored on your system hard drive. Each time you configure POP3 on a new device, only the additional emails will be downloaded. This saves time in configuring the email account.
  • In POP, opening and accessing attachments are quick because all the attachments are already downloaded.

Step by step procedure to convert IMAP to POP

To start this process, open MS Outlook and start the below-mentioned steps:

  1. Click on File > Info > Account Settings.

  2. Then click on New to add a new account.

  3. Select Manual set up or additional server types and then click to Next.

  4. Now select POP or IMAP and then click to Next.

  5. Enter your POP details and then click on More Settings.

  6. Then move to the Advanced tab and enter POP and SMTP port numbers and click OK.

    Note: Here, you have an option to leave copy of messages on the server for a definite period.

  7. It will take few seconds, and your POP account is successfully added to Outlook.

Steps to remove IMAP account from MS Outlook

After successfully adding your POP account, you can remove your IMAP account from Outlook.

  1. Click on File > Info > Account Settings.

  2. Then select the IMAP account and then click on Remove button, your IMAP account is successfully removed

Migrate IMAP to Cloud

Recently many users are migrating their IMAP email data to cloud emailing platforms like Office 365. This process is easy if you are using a third-party tool for migration.

Kernel for IMAP to Office 365 is a brilliantly developed and designed tool to migrate IMAP account to Office 365, hosted Exchange and on-premises Exchange. With this, you can quickly migrate those mailboxes which are configured with IMAP settings.

You can also migrate single as well as multiple mailboxes from IMAP email servers to Office 365. And this tool allows users to migrate emails to mailboxes, public folders and archive mailboxes in Office 365.

We as soon going to have to migrate off our current SBS 2008 Server. We are using the Exchange Server. The controller is concerned about the cost of moving the emails. $6 /email /month works out to $2880 per year for Office 365 email. For people who use basic email I must agree that is a lot. Are there other reliable options that don't cost as much as Office 365?

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.