Email Protocols




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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 got a mail from was it real or not please tell me
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This article outlines some of the reasons why an email message gets flagged as spam on a recipient's end.
I have one client that cannot email me.. They receive a bounced back message saying;

550 Verification Failed
No such user here
Sender verification failed

I can however email them. But they cannot reply.

None of their emails from their domain will come through, however I have been guaranteed from my ISP (crazy domains) that there are no blocks on my end. However i do know of another company who are with crazy domains are experiencing the same problem with the server  

As I run my ow  business, my only option is to change hosting companies in the hope that works.

Would love an easier fix
We have a web application that uses the client email to send email 'from'. We want to add an SPF record on the client's DNS (text records) to allow this. I need to confirm the syntax before I do so.

v=spf1 a mx ip4:XX.XX.XXX.XX ~all

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"domain" being their domain name
XX.XX.XXX.XX being the IP of the server that hosts the web application

Please let me know if you think this looks correct or if any changes are needed.. Also what is the difference between  and
Hi All,

May I know where shall I manually add the below entry if I handle the Public DNS using Windows Server box in my DMZ ?

DKIM: Create a CNAME record for with this value:

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SPF: Create a TXT record for with:
v=spf1 ?all

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What is the risk or issue when implementing it during the business hours ?

Had issues with ActiveSYnc timing out on Exchange 2010 SP2 RU4. Updated the server to SP3 RU17 on May 20th.
Only the activesync timeout problem for 3 Users existed prior to this update. These activesync issues remain for the three Users (not the focus of this question) and new issues are seen (focus of this question):

Total of 15 Users out of 250+ affected with this new problem. These Users are not the same with the ActiveSync issue:
1) For SOME Users all shared mailboxes in Outlook no longer populate with emails or auto-update immediately after the updates.
2) For SOME Users, this issue appeared to start a full week later.
3) For ONE User, only one of three shared mailboxes in Outlook are not auto-updating.
4) Selecting the folder in Outlook ,choosing the 'Send/ Receive' tab and selecting 'Download Headers' then 'Update Folder', allows the emails in these shared boxes to populate with new emails (since the last time this process was manually run).
5) Win7 Pro for all but two Users, who are on Win10.

What I have tried (not necessarily in this order):
1) New Outlook profiles
2) New Win7/ 10 User Profiles. Tried this because loading two of these Users' profiles onto a different, unused laptop works fine.
3) Deleting the .OSTs manually and rebuilding
4) Cached Mode/ Online Mode
5) Deleting the autodiscover xml record in the Outlook profile folder. Did this in case that file was corrupted and was not pulling the shared mailbox info properly.
6) Saw a …
Hey Everyone,
 This started late last week all of the domains we host are unable to send out to AOL but we can receive aol email.
Ive checked all of our domains against blacklist as well as the server IP.

Any ideas on this ? I'm completely lost at this point and still waiting to hear back from AOL.  Is there anything I can check or do to rule things out?
Our mail service is server 2012 running smartermail.
I am trying to setup subscriptions through our reports server generate reports and have them automatically emailed to external addresses.
I am using SQL Server 2012
Reporting Services Configuration Manager
Email settings:
Sender address:
current smtp delivery method: use smtp server
smtp server:

WE do not have a local smtp server setup so if I can use google smtp or some other method to send mails from the reports server that would be great.

Thanks for your assistance:

my not-for-profit has 20+ service-focused email accounts for different business needs. Right now I keep about 10 tabs open on my desktop to monitor incoming traffic and reply when needed. Is there an app/dashboard (like Hootsuite) which I could use to create dashboards to manage these Inboxes?

I have a domain a purchased through GoDaddy. I then am using HawkHost to send and receive emails. I changed the MX records accordingly.

For some reason, I can send messages but I can't receive them? Any idea what would cause this? Is there anything other than the MX records I should be changing on GoDaddy?

Also kinda strange... if I do the Outlook "Test Email" the message ends up coming through. That is the only message that makes it into the inbox.
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Dear Sir,

We have a software to send bulk emails to our clients which contains the course materials. When sending the bulk emails, there are lots of error/time-out which the destination mail server reject our emails. I've solved the problem for those by adding a record on our DNS server to proof we are not the spammer. But yahoo and hotmail not solved yet. Are they have this mechanism?

Thank you.

With regards,
recently my mail relay server experiencing incoming mail delayed from, as i see online forums, MS recently have stopped using TLS 1.0 authentication and only supports TLS 1.1 and 1.2, but not all of their servers but 75% of it, but my mail relay server doesn't have any TLS enabled, so is this can be the issue?

all the mails from other mail servers receive without any issue.

My mail relay server is CentOS 6.5 , (no Grey list enebled, no SPAM filter, no TLS enabled)
how can I download all my gmails for offline viewing
Is there such a list of IP or smtp domains (doesn't have to be up to the hour up-to-date) list so
that we can block at our smtp?

Blocking by firewalls is not good as the emails will still come in
What's the easiest way to move from pop3 to imap on multiple devices?
Pretty sure the mac stuff (iphone, ipad & possibly mac book) are currently using imap, but the PC (desktop & laptop) is the one that makes me nervous. I can envision myself with hundreds, if not thousands of duplicate emails to sort through when its all said & done!
I get an email in outlook 2016 through my pop mail server (if that matters), with the specific email I am looking at sent from gmail... but I think this is a generic question.

On the to line, along with my name, it might show 'steve smith'; 'bob jones'; etc.... the other people it was sent to, with each name in single quotes (this is a group mailing)

Each is a hyperlink - i can hover on a name and a little window pops up with the contact image (just the default outline), and the mail icon is clickable.  A down arrow brings up a bigger contact window with that person's email address.

My question - where is it getting all those person's names?  From the sender's contact list? or is it matching to my contact list? Don't think that's the case, 'cause I don't have some of those people.

and when I send an email, is it also picking up the person's name and including it along with their email?

If I was to have a contact for 'bob (what a butthead) smith'  with email, when I type an email to bob smith, does he see that name I have for him!?

Is there a way to keep that from being sent? so he just sees it was sent to
Hi Experts exchange.  I have an application that sends emails upon completing a arduous process.  Ie.. we have to create a permit and inspect it and what not for the email function to fire off from the application.  Our email functionality has been suspect and I was wondering if there was a quick and easy way to send an smtp request to our smtp server from a command line to quickly test functionality without having to create the permit and inspect it.
Does anyone know how to do this.
the server is windows 2012.

if someone could type the syntax or command, that would be awesome.

example variables you could use.   the sendto address is   the smtp server address is  the hostname of the server trying to send the email is bigsun with ip address

those are fictious settings above but just wanted to be able to tie logic to syntax.
Can someone help me out.
regular gmail; not g-suite. one label.

gmail label

only want gmails to reach inbox from one sender

all the other emails are not important

is there a gmail filter using the word NOT
If we have valid SSL cerfiticate for server/client authentication, is there any reason to have a TLS certificate?
Asking because I'm receiving the following event frequently in event viewer

"There is no valid SMTP Transport Layer Security (TLS) certificate for the FQDN of The existing certificate for that FQDN has expired. The continued use of that FQDN will cause mail flow problems. A new certificate that contains the FQDN of should be installed on this server as soon as possible. You can create a new certificate by using the New-ExchangeCertificate task."

Also should expired certificates be removed?
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We are receiving email from external whose email header display a different "Reply-To" address than the "From" address

such as

From: External User <>

To: Internal User <>

Reply-To: External User <>

The reply to is appending to our spam filter that we use for incoming and outgoing mail
Thank you in advance!
Hallo I recently move my company to Office365 and I add the SPF record as Microsoft provide. I would like to know if I will add +a to the SPF will work as I expect or I will have problem.
We have 2 AD sites, Exchange 2013 in each site and different domains in each site but same organization. When user in Site A with domain A send an email to external address plus a user in Site B with domain B, Server transfer the message to Exchange in Site B instead of solving the names and creating two copies of the message, one to transfer to Site B and one to be sent through Sent connector. All send connectors are scooped and we check Exchange servers to make sure they are in different Ad sites. If user in Site A with domain A send message only to external address it goes to the right send connector, the problem only occurs when a user from Site B with domain B is copied in the message.

Any help will be appreciated.
My OS is win 10 pro 64 bit and I have the Office 365 and use Outlook owa.  i managed to switch on Conversations and it is now very convenient as I am able to review the response I sent.  
But sometimes an email is outside the conversation, but it is relevant to that topic.  Is there any way I can lump them to a conversation.  Attached is an example.  i would like to add the email at 6.08 PM to the conversation below with the others.  Thank u for your response
My OS is win 10 prof 64 bit and I use Office 365 Business Essentials and Outlook owa for my Email client.  My email account is MSN the free version.  
I want to reply to an email, and in this response, I would like to embed a previous email from Inbox.  Can this be done, and if Yes, can the Experts kindly show me how it is done.  Thank u.

Email Protocols




Articles & Videos



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.