A Better <CFMAIL> | SYS-CON AUSTRALIA

A Better

Sep. 11, 2003 12:00 AM

One of the most used tags in CFML is <CFMAIL>. It is definitely the most used of all the Internet protocol tags, and as one of the original CFML tags (it was actually one of the DBML tags and originally named <DBMAIL>), it has also been slowly enhanced and updated with each new release of ColdFusion. Slowly. Maybe a little too slowly.

ColdFusion MX 6.1 introduces a whole new <CFMAIL>, a much better and much more powerful <CFMAIL>, and this month I'd like to walk you through these important changes.

Improved Performance
Let's start with performance. <CFMAIL> was never designed to be a high-performance mass mailer, and yet many developers have tried using it as just that. <CFMAIL> has always been very capable of delivering hundreds, even thousands, of messages, but that's about as far as the tag could be pushed.

ColdFusion MX 6.1 introduces important changes to the <CFMAIL> engine that facilitate dramatically increased mail-delivery performance. In fact, in testing, we clocked <CFMAIL> on a fairly typical box delivering mail at over 1,000,000 messages an hour (so fast that the bottleneck became the network and mail server rather than ColdFusion).

So what changed? Two things:

The ColdFusion mail delivery engine now supports the use of multiple mail delivery threads. What this means is simply that ColdFusion can create multiple processes, and each can deliver mail at the same time. So, instead of just one thread processing all queued mail, multiple threads can do the job, and that translates into greater mail throughout. The number of threads defaults to 10, but you can change this number in the ColdFusion Administrator. Each thread requires system resources (some memory and a bit of CPU power), but the overhead is actually minimal and only present during mail delivery itself. As such, if you need to deliver large amounts of e-mail quickly you can raise this number as needed; the greater the number of threads ColdFusion can allocate, the more mail it can deliver concurrently. (The number specified is a maximum value; ColdFusion may actually allocate fewer threads if there's not enough queued mail to warrant all threads being allocated.)

When ColdFusion delivers mail, it connects to an SMTP server and disconnects when done. It does this for each and every message. And the process of locating the server, opening the connection, and then closing it when done, often takes longer than the actual mail delivery. Or rather, ColdFusion used to do this. In ColdFusion MX 6.1 there is a new option (in the ColdFusion Administrator) named "Maintain connection to SMTP server", and when checked, ColdFusion keeps connections open so as to be able to reuse them for subsequent message delivery. Not having to keep making and breaking connections improves the delivery time for each and every message, so unless you have a very compelling reason not to, you should keep this checkbox checked.

<CFMAIL> performance has been improved in all versions of ColdFusion, but if you need high-volume mail delivery, then you should be using ColdFusion MX Enterprise. The two changes just described apply to ColdFusion MX Enterprise only.

Server Redundancy
One frequently requested <CFMAIL> enhancement is support for backup SMTP servers so that if a mail server is down, a backup SMTP server would be used. Support for redundant (backup) SMTP servers has been added to ColdFusion MX 6.1 Enterprise (this too is an Enterprise-only feature).

ColdFusion Administrator contains a new field (in the Mail page) named "Backup mail servers". You may specify as many servers as you like here (DNS names or IP addresses) in a comma-delimited format (you may also list backup servers right in the <CFMAIL> tag SERVER attribute). The specified servers are the backup servers, and will be used automatically if the primary SMTP server is unavailable.

It is important to note that <CFMAIL> does not support multiple mail server delivery. These additional servers are backup servers and are used only if the primary server is unavailable. If a server (any server) is unavailable, then ColdFusion will attempt to use the next server in the list. Once a server has been flagged as unavailable, ColdFusion will not attempt to use it again for 60 seconds. If all servers are unavailable, then an error is logged.

Like the high-performance features discussed above, the ability to specify backup SMTP servers is an Enterprise-only feature. (From this point on, however, everything discussed applies to all versions of ColdFusion, including ColdFusion MX Standard).

SMTP Security
SMTP was never designed to a be a secure protocol. As we are all painfully aware, you can never really be sure who mail comes from and whether or not a FROM field contains the actual sender address. It's all too easy to submit fake SMTP e-mail to mail servers for processing.

In recent years, mail administrators have started taking steps to prevent their servers from being used to deliver unauthorized mail (commonly known as relaying). One technique that has gained popularity is to require an SMTP login. Unlike POP, which always requires a login, SMTP usually does not, but many SMTP servers now do require that login credentials be passed in in order to deliver outbound mail. If enabled, this security prevented the use of <CFMAIL>, as <CFMAIL> provided no way to specify login information.

ColdFusion MX 6.1 supports SMTP logins in two ways:

The <CFMAIL> tag has two new attributes named USERNAME and PASSWORD. You may pass SMTP login information to these attributes, and <CFMAIL> will use this information to log in to the SMTP server.

You may also specify login information at the server definition itself (so as not to have to pass it to every <CFMAIL> tag). Login information can be specified in the ColdFusion Administrator as part of the server name. The syntax for this is modeled on the syntax used by many Web sites: user:password@hostname. If you specify backup SMTP servers, you'll probably want to provide the login information for each and every server (assuming that they all require SMTP logins).

The ability to use SMTP logins is an important enhancement, and one that will make many server administrators very happy.

Multiple MIME Types
One of the most eagerly anticipated <CFMAIL> enhancements is the ability to include multiple bodies of different MIME types all in a single message. What does this mean? Consider the following:

You deliver reports via <CFMAIL>. Your reports are detailed, have columns, colors and fonts, use images, and more, and so you tell <CFMAIL> to deliver the e-mail in HTML, as most mail clients, including Outlook and Outlook Express, support HTML e-mail. The problem, however, is that not all users have mail clients capable of displaying HTML e-mail, so you also need to generate a plain-text version of your report for those users. Of course, this then requires that you maintain a record of which version to send to which user (probably a flag in your database). You'd need a way for users to specify the message type they'd like, and then mail generation code that might look a bit like this:

<CFIF user.htmlmail>

<CFMAIL TO="..."
FROM="..."
SUBJECT="..."
TYPE="html">
<B>HTML body</B>
</CFMAIL>
<CFELSE>

<CFMAIL TO="..."
FROM="..."
SUBJECT="..."
TYPE="text">
Text body
</CFMAIL>
</CFIF>

You'd need to repeat everything, not to mention maintaining the user mail preferences. You'd also not be able to use the <CFMAIL> query attribute easily, or you'd need two queries - one for text message recipients and one for HTML message recipients - and then you'd need two <CFMAIL> tags (one for each query).

There's a better way to do this. E-mail messages can actually contain multiple bodies, each of a different MIME type. The problem is that <CFMAIL> did not support the use of this feature. Until now, that is. Here's the ColdFusion MX 6.1 version of the previous example:

<CFMAIL TO="..."
FROM="..."
SUBJECT="...">

<CFMAILPART TYPE="text">
Text body goes here
</CFMAILPART>

<CFMAILPART TYPE="html">
<B>HTML body goes here</B>
</CFMAILPART>
</CFMAIL>

As you can see, a single <CFMAIL> tag is being used along with two instances of a new tag named <CFMAILPART>. This new tag allows you to embed multiple bodies in a single message, as long as each has a different MIME type. This way it is the mail client that decides which body to display, and this makes your life a bit simpler. (It also means that your mail messages will be bigger; you'll need to decide whether or not this is acceptable.)

Any and all MIME types are supported, although in practice you'll probably use only TEXT and HTML.

Note: Although we're just covering <CFMAIL> in this column, it's worth noting that <CFPOP> has been similarly enhanced and now supports the retrieval of multiple bodies as well.

Other Enhancements
In addition to all the changes listed thus far, <CFMAIL> also features lots of little enhancements. Some worth noting are:

A new REPLYTO attribute, which can be used to specify the e-mail address to which replies should be sent (previously replies would have been sent to the FROM address).

A new FAILTO attribute, which can be used to specify the address to which SMTP delivery failure notifications should be sent. This is an important attribute for mailing list-type applications.

A new CHARSET attribute, which can be used to specify the character encoding to be used for the mail message (overriding the default encoding specified in the ColdFusion Administrator). This attribute is present in both <CFMAIL> and <CFMAILPART>.

A new WRAPTEXT attribute, which can be used to force a wrap (a line break) at a specified location within text messages. This attribute is present in both <CFMAIL> and <CFMAILPART>.

A new TYPE attribute in <CFMAILPARAM>, which can be used to specify the MIME type of file attachments.

Conclusion
<CFMAIL> is an important ColdFusion tag and ranks as one of the most used tags in the CFML language. For high performance and high-availability mail delivery you should definitely consider using ColdFusion MX Enterprise. For all users, the enhancements to this tag in ColdFusion MX 6.1 provide yet another compelling reason to upgrade.

* * *

On a totally separate note, this is my 50th CFDJ <BF> on <CF> column - that's 50 back-to-back columns (with only one exception, and I'll try not to let that happen again). While writing this column, I glanced at the topics covered since way back when, and was reminded of just how far ColdFusion has come in such a short time. It's been a great ride thus far, here's to another 50!

About Ben Forta
Ben Forta is Adobe's Senior Technical Evangelist. In that capacity he spends a considerable amount of time talking and writing about Adobe products (with an emphasis on ColdFusion and Flex), and providing feedback to help shape the future direction of the products. By the way, if you are not yet a ColdFusion user, you should be. It is an incredible product, and is truly deserving of all the praise it has been receiving. In a prior life he was a ColdFusion customer (he wrote one of the first large high visibility web sites using the product) and was so impressed he ended up working for the company that created it (Allaire). Ben is also the author of books on ColdFusion, SQL, Windows 2000, JSP, WAP, Regular Expressions, and more. Before joining Adobe (well, Allaire actually, and then Macromedia and Allaire merged, and then Adobe bought Macromedia) he helped found a company called Car.com which provides automotive services (buy a car, sell a car, etc) over the Web. Car.com (including Stoneage) is one of the largest automotive web sites out there, was written entirely in ColdFusion, and is now owned by Auto-By-Tel.