In IE, if you click on the "Mail" icon on the toolbar - a little envelope with the flap open - you can choose "Send a Link" or "Send Page."
If you select "Send Page," the web page you are viewing is inserted as body text into a new email message. The message received, at least in OE, looks very much like just looking at a mudcat thread.
This thread, through Clinton's post at 01:04 PM, is received in OE as a 58 KB email. There's a bit of "overhead" in the page, so the size isn't strictly proportional to the number of text characters, but is roughly so. The size of the email received is NOT necessarily the same as the size of a "saved page" if you use some method other than sending the page as an email to yourself.
If you select the "Send a Link" option on the mail button in IE, the link appears as an attachment. The attachment itself, in this case, is about 85 bytes, and would be about the same size for a link to any thread at mudcat. The email containing the link as an attachment shows, again in OE, as about a 3 KB message, if you leave the default text in the body of the message.
Many email filters (spam filters, mostly) automatically reject email with attachments, unless you've specifically declared the sender to be a "trusted source."
Some email filters pretty generally reject email containing links, again unless you've specifically declared the sender to be a "trusted source."
Some email programs and/or email services, by default, prevent sending email containing links unless you make appropriate changes to your email settings.
A link as an attachment should be doubly suspect, although I don't know what rules generally are used by common filters. The "threat potential" comes from there being no simple way to see what the link is except by opening it, so if you click the attachment you execute any connection the link wants to send you to. "Faking," where the link looks like it will send you to a good place but actually sends you to a malware site is very common in spam, and some filters may reject mail on this basis.
If you "Send a Link" OE inserts the default text in the body of the email:
"The message is ready to be sent with the following file or link attachments: Shortcut to: http://www.mudcat.org/thread.cfm?threadid=81389&messages=13
"Note: To protect against computer viruses, e-mail programs may prevent sending or receiving certain types of file attachments. Check your e-mail security settings to determine how attachments are handled."
You may get a different default text, or none, with other email programs.
With respect to file size - many email providers limit the size of single messages you can send and/or receive. Usual limits on individual messages are 1 or 2 MB, although premium services may allow much larger messages.
Many providers also limit the total amount of stuff you can have in your in box or on the server. It is not necessary, in the latter case, that your message be particularly large if it brings the total of all messages in the recipient's inbox to more than the provider allows -- the message will be rejected. As noted above, a couple of dear (cheap) friends often bounce 20 KB messages because their boxes are full.
The simplest way to look at what's happening, when there's an email problem is to send a message to yourself and see if it gets through. If you're having problems sending to a particular recipient, adding yourself as a CC: or BCC: to the message will tell you whether the problem is yours or the recipient's. If you get the CC:, then the mail was sent and was blocked or fumbled at the recipient's end.
Some, but not all, email providers routinely send a "non-delivery" notice if a message is not delivered. Rarely, these may give some indication of what went wrong; but usually they're just a notice that the message didn't go through.
As an incidental note, the same IE mail utility can be used to send individual images from a web page. You can put "email" in the search line in IE Help to see other things you can do.