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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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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!
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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: smtp.emailarray.com  Port: 587
Login: info@computerohio.com

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 "smtp.emailarray.com" 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: auto@abc.xyz

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!
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 @mydomain.com pointing to the IMAP server via its MX record.  Setup Office365 to a subdomain @admin.mydomain.com 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 @mydomain.com 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.
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
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 include:spf.protection.outlook.com -all

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

Thank you,
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Hello Experts,

I am working on a small website that allows users to send a vCard (.vcf file) to an email address they specify. The coding for this function is in php, and I should mention that my php skills are pretty basic. There are 2 versions of the email that sends the vCard: one in English and one in Japanese.
So far, everything is working fine, except that on Android smartphones, the Japanese characters in the subject line of the email get mangled (the body text is fine). It is obviously a character encoding issue.
Researching the issue on google indicates that I need to specify the character encoding for the subject text (in the case of Japanese, I think this would be UTF-8). I have tried a number of things to achieve this, but just cannot get it to work.
I provide the code as an attached file. I’d greatly appreciate it if anyone could have a look at this and let me know of any suggestions for a solution to this. Thank you in advance for any help.
Hi All,

Can anyone here please let me know what do I need to do in order to successfully cutting over the Anti Spam solution from onPremise Linux VM into the Cloud Solution with no data loss or user email flow interruptions?

As at the moment on my Exchange 2013, the Send Connector Smarthosts listing the local IP address for the 2x Linux VMs.

Do I just change it to the Public IP address of the Cloud Anti-Spam provider ?

Note: My Public DNS server is running on my On-premise Windows Server 2008 R2 VMs.

Dear Wizards, when I changed my display name in OWA - Exchange 2016 ono-premises, this error appeared. Can you please explain and suggest? Many thanks.

Env: Exchange 2016 - Win server 2012R2
Dear Experts, I am wondering if we can monitor the usage of users' mailboxes in Exchange 2016 Server (Win2012R2), just like we usually monitor servers, network devices,...; so that we can have proper actions when someone nearly reach his/her quota.

Do you know any tool or procedures to do that? Many thanks in advance
Dear Experts, can we create a distribution group which contains email accounts from different domains (than the server's domain)? If so, how can we configure it?

Example: Exchange 2016 server for domain abc.com

Can we create a distribution group that includes?
- user1@abc.com
- user2@gmail.com
- user3@xyz.co.uk
Dear Experts, does anyone know how to monitor the email flows from users (like statistics, how many email per day, per hours each user send/receive,..) in Exchange 2016 environment? (Server 2012R2)

Besides, is there any option so that we can limit that number, to avoid hacker can login to email account and send huge number of spam emails to outside, leading to blacklist our domain?
Dear guys, is there any public black list like this? we are building our own Exchange server and want a list of black domains; so that we can configure antispam agent on Exchange to block them.
Dear Experts, can we delete the log files in %ExchangeInstallationPath%\Mailbox\DB ?

We observed and saw that they increases everyday. If we cannot delete them, how can we reduce their size?

Env: Exchange 2016 Mailbox server, Window server 2012 R2
Anyone know the SMTP authentication for San.RR.com?   I'm also not well versed in Apple Mail client so I may be doing something wrong.  I referenced below but I don't see SMTP authentication... My options are External, Kerberos, NTLM, MD5, and Password.  Also, do I need need a IMAP path prefix ?

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Dear Team, we are suffering the slow problem of Email Exchange 2016: Send from Exchange server is OK, but receive is slow; which ever have or does not have attachments.

We have Avast installed in Exchange server, everything in default mode, not sure which Exchange part should be added to AV's exclusion.

Is there any other way for tuning or increasing the speed (except increase the bandwitdth, we are in Leased line link: 30 Mb/s International + 50 Mb/s Domestic)?

Many thanks as always!
Can one add a hyperlink to fields that when clicked not only creates an email but can fill in the other email fields like CC, Subject, and Body?

I have done this in excel, but not sure if the hyperlink format formula editor in crystal reports can handle this.

What I did in excel:

HYPERLINK("mailto:"&$A$1&"?cc="&$A$2&"&subject=TRD INQ: "&B9&"  |  "&E9&"  |  "&F9&"%  |  "&I9&"  |  "&H9&" &body=CUSIP: "&B9&"%0AAmount:%0AAccount:%0ASub Account:%0A%0ADealer: "&Y9,"SEND")

this excel formula handles creating the email and populating the To, CC, Subject, Body.
I have an enormous problem about my disk quota .
Everyday tons of emails enter my mailboxes
I have a plan to pull all my email to sync in local folder. So my i can freed my corporate email
Are there any tutorial to pull all of my corporate email via Thunderbird ?
POP3 or IMAP kindly accepted


Romi Nur

We have a client who has just had a DKIM domainkey setup for them. Unfortunately some emails are not getting through to the end users (especially if using Mimecast mail servers).

We have been doing some testing and have found that:
Emails that do not have an attached file - it pass the DKIM checks.
If emails have attached documents, they seem to pass OK as well.
If emails have got an attached email that was originally from the sender, it passes OK
If an email has an attached email from a third party (that has originally been changed with DKIM) it fails the DKIM test on our/the recipients servers. This has happened to us and we use exchange online servers.

When it fails it says dkim=fail (body hash did not verify)

They have a valid SPF record also setup and every email through the testing procedure seems to pass on the SPF checks without any failures.

There is no DMARC record setup yet, but as far as I can see this is the next step after we have got DKIM working correctly.

Unfortunately our client who is having this problem quite often forward a lot of emails during their working day so need this resolving.

Any help would be appreciated.
Dear Guys, please assist this scenario:
- Action: We changeed Email server from Gmail to Exchange 2016 On-premise, so we had to change the domain records in Domain control panel. We changed TXT, MX, @, mail records.

- Problem: After changes, the new Exchange server worked (send/receive emails) normally as expected, however we realized that we could still login to Gmail account, Google Drive and sent emails (but could not receive emails)

So can you please explain?
Dear, I tried but could not start this service. Does anyone get this error before? Can you please help?
Many thanks in advance,

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.