The first thing you need to understand is that almost all email clients require an email server. That is, when I address an email to you, it doesn't go directly to you - my email client sends it to its email server and that server sends the mail to your email server, which is where your email client finally gets it from. There can even be more servers in between mine and yours.
Any of the servers - mine or yours or (in rare cases) anything in-between - can have policies in place that affect attachments.
For example, one of the people who commented at yesterdays article notes that his business server explicitly rejects Microsoft attachments - you simply cannot send such things to anyone at that business. Certainly that is unusual, but other restrictions are quite common.
For example, Gmail (and many others) won't allow you to send an ".exe" file as an attachment. Many servers won't receive such an attachment anyway and many email clients would also object, so Gmail's refusal is just the beginning of difficulties you might have in sending such a file (although it is easy to circumvent simply by renaming the file in most cases).
Servers may also examine attachments for hidden viruses and (rightfully or wrongfully) reject them if they think they are contaminated.
Attachments can also run into roadblocks because of size. I had a family member who tried to send several dozen pictures in one email attachment. While some email servers will happily do that, the recipients server imposes limits on how large an individual email can be, so that email could not be delivered. The solution is simple enough - break it up into multiple emails.
Size issues can be a bit confusing. You might have been told that your server won't allow attachments over 10MB and yet have an 8 MB file rejected. That's because attachments actually have to be converted into a text based code and that conversion requires additional bytes - your 8 MB file could easily be more than 10 MB after encoding.
Why can't I open the attachment my sister sent me?
First, is it really an attachment? If you are not an Outlook user, you may have noticed mysterious "eml" attachments in email sent to you by other people. These aren't actually attachments, they are Microsoft "stationery" files which provide decoration for other Outlook users. You can't open the attachment because there is nothing for you to open - just ignore those.
If it really is an attachment, it's also possible that Outlook or Outlook Express could be set not to allow opening of attachments. See if Tools->Options->Security "Do not allow attachments to be saved or opened that could potentially be a virus" is checked. Some versions of Outlook deliberately prevented the opening of certain types of attachments to protect you.
More common is that you don't have the program you need to see the attachment. For example, years ago many people got Microsoft Works free with their computer. As I live in a retirement community, I see that fairly often. If someone sends you a "Works" attachment, you won't be able to open it if you use Microsoft Word. There is a conversion program you can get from Microsoft that will let Word read Works files, but you have to download it. If you don't have either, you may be out of luck. Get your sister to cut and paste whatever it was she wanted to send you.
I am regularly amused by people who have replaced their computer and now can't get their email because they can't remember their password.
Many stridently insist that they never had a password! Of course they did, but it was memorized by the computer that is now being disassembled at a recycling plant.
Well, you hope it is being recycled. If not, the next person to turn it on can send email to everyone you know.
By the way, this is one of many reasons why I recommend never letting your computer memorize any password for you. If that computer is lost, whoever finds it immediately has access to everything of yours. Also, when you fire up its replacement, you may have no idea of what any of those passwords were, so they'll all need to be rest. If your computer was stolen, of course you'd want to do that anyway, but that wouldn't be necessary had your machine just died suddenly.
Your email password could get hacked
To avoid that, don't use email at wireless hot spots unless you are typing on an https connection (webmail) or are using secure authentication (pop, imap). You can tell Gmail and some other web based systems to always use https (that's in your Settings and it can be a smart thing to turn on). Other providers may have similar options; you really should check because it can save you from a careless and potentially costly mistake.
Why does Webmail mess up everything?
It doesn't, but I hear this question fairly often. Somebody has Outlook but they used Webmail and now they are all confused. The reason is simple, and it isn't Webmail that is at fault.
Most Outlook accounts get set up as POP because that's the default. You may not have even noticed that you had a choice at all, but you did. Your email server probably has IMAP available, but because Outlook defaults to POP, that is what gets used.
That's a problem if the mail server also offers Webmail access as many do today. The reason is that (by default) POP retrieves mail from the server, brings it down to your computer and then deletes it from the server. If you then go look at mail using Webmail, that email that was POPped is gone! That's confusing at best.
But there's even more confusion caused by POP being unable to see folders created on the Webmail server. Those emails are just completely invisible to POP. All POP knows about us the INBOX.
There are two ways to fix that. One is to tell POP NOT to delete mail until you delete it on your computer. That can be set in the Advanced section of the account settings. That will solve part of the confusion, but not the "missing" folders. There's a better choice, and that's to switch to IMAP, which works just like Webmail - it won't delete mail from the server until you delete it yourself and it will let you see the "missing" folders.
Why is mail stuck in my Outbox?
If it is just one email, it could be misaddressed. Look at the address carefully - you may have mistyped it (comcat.net instead of comcast.net for example). I often see things like "mary,@gmail.com" - that comma shouldn't be there.
The recipients server could be having temporary problems; the mail may be able to go later.
If it's more than one message stuck, you start with the obvious. Is your Internet connection working? Can you still browse the Web? If not, email can't get out, so that's why it's still in your inbox. See my Guide to Understanding Network Problems for assistance.
Don't forget that your A/V software can interfere with sending and receiving email. It can be worthwhile to temporarily shut that off just to check. If that is the problem. of course you then need to find out how to fix it, but at least you know what caused it.
I sent email to John but it can't be delivered. Why?
Assuming that you didn't mistype and that John still has that email address, there are still other reasons why John won't get your mail.
We'll also assume that John hasn't deliberately blocked you because he's sick of the dumb jokes you are constantly sending him.
It is possible that you could be "blacklisted". That's where the receiving server thinks your email server are guilty of sending spam. This can happen with Gmail, Comcast, Verizon.. they'll get it fixed very quickly, but it can be very annoying for you. In this case, you will usually (but not always!) get a message back that says you were blacklisted. If you are running your own mail server, pay attention to that message because it usually tells you what you might be able to do to get off that list.
John's spam filters or mail rules may have put your email in JunkMail or somewhere John forgot to look. That's John's problem, but you might call him up and remind him to check.
John may have a quota that restricts the number of messages or their total size. You might get a return email telling you that, but you might not. John should know if that's the problem, right?
As I said above,, John's email server might just be down right now. You'll almost certainly get a message from your server if that happens. Sometimes that message just tells you that there's a delay and your message will be attempted later, sometimes it tells you it has given up. If it gave up, and you know the address is correct, try it again tomorrow. Or call John and ask him what's going on with his email.
I got an email that said my mail to somebody couldn't be delivered but I never sent it. Do I have a virus?
More often someone you know has the virus. What happened was that the virus found your email in their address book and is sending out junk that pretends to come from you. Anybody can send email that pretends to be from someone else.
Sometimes someone you know will say that that got a virus message from you. Sure, your computer could have sent it, but it might also be a computer owned by someone you both know.
One way to tell is to look closely at the original email message. You don't usually see all of it, but your email client has some option like "Show Original" or Show Headers" that will show you everything.
You want to look at the "Received: from" lines. The very last one is the one that could exonerate you. For example, if that says "Received: from [127.0.0.1] by dazzler.dsl.net" and you connect through Verizon, that email is unlikely to have come from you. It is still possible, but it just became far less likely.
If your ISP blocks outgoing mail connections to everywhere but their own SMTP server (just ask them) and that email went out through some other server, it definitely did NOT come from you. Your friends may insist it is, but it wasn't. There's nothing you can do about it.