If your message is split into multiple parts, you have either exceeded the standard 160 character limit or there's a Unicode character present in your message. Unicode characters use more data to send than regular characters. Therefore only 70 characters can be included in a single SMS, as opposed to the standard 160 character limit.
When you exceed the standard 160 character limit, your message will be split into a multi-part message. Seven (7) characters are needed to stitch the messages together, leaving you with 153 characters to work with per SMS.
1 message = 160 characters
2 messages = 306 characters (153 + 153)
3 message = 459 characters (153 + 153 +153)
When sending a message in MXT, do not copy and paste your message from a word document or anywhere else. Instead, type the message directly into the box provided to avoid adding Unicode Characters.
Before sending your messages, please ensure that you look at the preview message on the right side of the screen.
This will show if your message has been split into a multi-part message:
The message box in MXT will also alert you if any Unicode characters are detected: