By Raj Choudhury

Ensuring your SMS messages are compliant with carrier rules is not as straightforward as you would think.

The level of inconsistency and mixed interpretation is mainly due to a lack of oversight and standardization in the industry.

In order to avoid costly lawsuits such as Timberland's $7 million, carriers have attempted to protect themselves, which is ultimately positive for consumers, but a pain for marketers.

When sending SMS messages to subscribers across multiple carriers -- AT&T, Verizon, T-Mobile, et cetera -- it is very difficult to conform to the exact requirements without knowing which carrier each subscriber is using.

For example, carriers require an opt-out message such as "Text STOP to Unsubscribe" and a message telling subscribers they might get charged for the SMS.

In this instance, the exact requirement from Verizon is, "Standard message charges apply" and for T-Mobile it is, "Other charges may apply."

Not knowing which carrier the subscriber is using makes it easy to violate this requirement.

To be fair, I am sure the carriers lend a blind eye to which version you use as long as it says something close, but technically, you may be breaking one or more carrier's requirements.

It's standard to ensure that these types of messages appear on initial subscription confirmation and system transaction messages, such as "text HELP" and "text STOP."

Most marketers assume that once they have provided this initial notification to the subscriber, it is acceptable to use the full 160-character message allotment for their message. However, this is not quite the case.

An examination of what Verizon and T-Mobile require for Mobile Originated ("MO") messages or transaction responses (that is, someone texts in a keyword and receives a response), reveals that these messages must include the "Standard message charges apply" for Verizon and "Other charges may apply" for T-Mobile in their total characters.

Effectively, what this does is reduce the available characters from 160 to 128 in the case of the Verizon example, if you add a space or hyphen to separate this from the rest of the message ("-Standard message charges apply.").

This adds up to about 20 percent less copy. If you require as many characters as possible don't follow this clause, I'd suggest using acronyms instead; "-StdMsgChrgsAply" or "-OthChrgsMayAply" which is 16 characters, or 10 percent of the 160-character allocation.

To illustrate this point, here is a hypothetical situation.

A commercial airline could provide customers a free flight-information service. Subscribers might text their flight number "DL323" to 33581 and receive a message back on the status of the flight.

Because this is considered an MO, the commercial airline must put "Standard message charges apply" at the end of every message, even if the subscriber has SMS'd 10 times in the same day to get the flight status.

Ultimately, it doesn't matter if only one carrier has a rule and the others don't.

To be safe, you're better off ensuring all messages conform to the tightest of requirements, especially if you don't know the exact carrier the subscriber is using and you want to avoid complex business rules with your SMS technology provider.

Furthermore, it is likely other carriers will follow suit soon and perhaps require tighter rules on all SMS messages regardless of the type of message.

Ideally, the industry needs to receive consistent standards and regulations in order to simplify SMS message requirements.

If you think about it, it's not that different than the inconsistent ISP rules we had for email marketing before CAN SPAM.

I hate to say it, but perhaps we may need more lawsuits before SMS spammers destroy this medium, and carriers get even more confusing.

Raj Choudhury is vice president of digital services at Engauge Digital, an Atlanta-based firm that specializes in branding, digital and direct marketing for national and global brands. Reach him at .