My U.S. web-based scheduling and address book program has the functionality to send one-way messages via SMTP to SMS. IOW: My program sends out an email - and it arrives as a text message to the cell phone address - eg: email@example.com (AT&T wireless).
If the message is over 160 characters, AT&T simply breaks it up into multiple messages. All of the characters arrive safe and sound - but spread out over the multiple messages. Verizon will receive only 160 characters of the message and aborts the remainder of the characters. Sprint will only receive the subject line - but none of the content. I haven't checked T-mobile yet.
The goal is to have the entire message received by any carrier - just like AT&T. We modified the program such that we tell each carrier to allow only 160 characters at a time. Now, Verizon successfully breaks the email up into multiple text messages - but, we lose around 15 characters between each succeeding message. This is better, but still not good. The lost 15 characters can have important data.
I think the limitation is in the handset or modem for receiving sms message. The standard is 160 characters as mandated in some codes. But some units now can receive more than 160 chars but still the sending and receiving is done by 160.
Perhaps if the standard maximum number of characters be changed, then we can have it increased.
Unfortunately, it's not just a handset or modem problem. Thanks to our programming modification, we can vary the number of characters. We've tested sending above and below 160 to different handsets. The problem appears to be carrier-related. Each carrier appears to have a different protocol as to how they transfer an SMTP email to SMS text message. But, still not sure what's going on.