Over the past 4-5 years there have been some strange issues with email. I have had to dig quite deeply into the protocols and supporting services to make sure that any third party receiving mail from the mail servers we use have access to responses that show the mail server is legitimate.
For the most part 99.99% of it works without any issues. I have come across problems with BT accounts (all of the BT family) where changes have been made to their mail processing, suddenly things stop working or become intermittent. I use BT for my broadband, but I do not use my BT address because I know some mail may get filtered coming into it. The problem is you don’t know about it. I have never set up any filtering, so this is a BT unilateral decision. From time to time there have been issues with the Talk Talk family of addresses and AOL.
The reasons why these service providers are trying to filter mail is the sheer volume of junk mail that is around these days. Occasionally the wrong things are filtered. The rest of this post is about things you can try if you think mail is being filtered.
Server Policy Framework (SPF)
One of the key responses that needs to be set up at the sending mail server is an SPF record. This provides information to an inquiring receiving mail server, that will try to establish whether the mail was sent from the appropriate email server. This is trying to detect “spoofing” where a 3rd party email server has sent something, not the legitimate server. This is something hackers like to do. They will take over a mail server and use it to flood mail out to the Internet.
If there is a problem the sender will often get a message back about the mail being rejected. If you see one of these send it to me. All accounts have an SPF record set up.
Blacklisting
Some receiving servers check whether the sending server is on a blacklist or not. If the mail server is on a blacklist the mail may be rejected. You will normally receive a message back to advise you of this. If you see any of these, raise them to my attention immediately, and I can flag it to support.
Mail servers are blacklisted because of the activities of some of the users on the mail servers. There are honeypot traps set to identify spam sources. If the server is identified as a spam source, it may be temporarily blacklisted.
You can independently check to see if your mail server is blacklisted by entering the domain name from your email address in this website: http://mxtoolbox.com and select blacklist check after the initial test has completed.
How to establish where a problem is
The system for handling emails starts with the mail program the sender is using. This sends a message to the outgoing mail server in a data centre. This is defined in DNS settings, and is not necessarily the mail server in your hosting, it is quite legitimate to use a 3rd party if you choose to do so. Mail leaving the sending mail server undergoes some checks in the hosting company before it leaves the data centre. Hosting companies can flag mail as being suspect before it exits the data centre, it can also limit the volume of mail, and even stop mail from being sent.
Mail leaves the data centre and is sent over the internet to the receiving mail server. Checks may be performed as the mail enters the receiving data centre. Checks may also be carried out by analysing the content, and where it came from to establish if it is a genuine email or not. If the mail was accepted it is placed in the receiving mail server. It waits there until the recipient hooks up to the internet and downloads the mail. If they are using a mail program, or an add in mail program this may assign the mail to a junk email folder, so even if it reached you, it might not be where you were expecting it to be.
Did it leave the hosting?
The first thing to check if someone is claiming that they did not receive your email is whether it left the hosting. Was it filtered before it left? To do this send a message to both the person who is having problems receiving your email, and to a third party address not associated with the hosting, say a gmail, yahoo or hotmail address.
If the message is received by the 3rd party account (gmail, yahoo or hotmail) then it left the hosting. Check to see if it is marked in any way as spam. If it is not, then there is no reason why the person should not be receiving the email unless there is a problem with their hosting company, in their mail server, or in their mail application.
The assumption is that it was never sent, that was why it was not received. This step proves that at least at your end it is all working.
I receive mail from everyone else!
Your recipient may claim that they receive mail from everyone else. The problem here is that this claim cannot be substantiated if you cannot detect that mail was not received. At the end of the day you don’t know what you don’t know!
I have personally been in this position with BT, and could not send a particular email to my BT account. I could see it was being filtered by a device in London with an obscure rejection code that nobody knew what it meant. I went through two levels of support with BT, and all I got back was BT did not have a way of contacting the people in BT that manage the filtering. When this has happened in the past, it is normally transient, and not a permanent problem. I would guess that someone somewhere has changed something in one of the parameters on the device.
Check the mail client
If we assume that there are no warning messages on why an email had not got through the problem is likely to lie in the recipient’s email set up locally on their computer.
The first thing to check if it is not arriving at the computer or device is to access the mail server through a webmail account if they have one. This rules out anything that is happening in the client PC or device.
If the mail is in the inbox on the server, but not locally on the PC, then this indicates a problem in the configuration of the PC. Do note here that mail application set up may delete the message from the server when you use your mail application. So if this is the case, do not use your mail application locally, ask for an email to be resent and check to see if it is received.
Also check whether you have a spam program operating on the server. If you have check to see what the rules are for filtering, and relax the rules if you cannot see the email coming in. Right now you are trying to find out where the problem is, not fix it. If the problem was down to mailserver filtering, then examine the settings to establish why. It may be that your settings are too aggressive.
If it got to the inbox on the server, but not locally you now need to look at your local configuration.
Add on Mail Filtering
Some anti virus and security products attach themselves to your mail application. These may be filtering mail. Temporarily turn them off and retest.
If they are the cause of the problem, the settings are probably too aggressive or try whitelisting the senders email address so that it is accepted rather than rejected.
Outlook
Outlook contains some features for handling blacklists and whitelists. It is possible that Outlook is mishandling your email. Look for this screen and make sure you understand the settings, set them to the lowest values and see if mail is still being filtered.
You can reach this screen by going to Home, Junk Mail, Junk Mail Options (see below)
Other things you can try are to highlight an email, and go to Home, Junk, and choose Never Block Sender if the selected message was going into you junk mail folder, this step should leave it in your inbox.
What else can I try?
If your mail application was supplied or set up through a third party, you can approach them and ask them what to change. Especially if it has been proved that the mail message was sent, others received it, but you did not.
Looking for Clues
One of the most important aspects to identifying what is happening with email is to collect any warning or error messages. Irrespective of how obscure they may be. While you may not understand them, someone else might. If you have some evidence of something not working properly, send it to me.
It is unusual to have email issues without any warning messages.