email@example.com. If the person uses Sprint for phone and text messaging service, you would append @messaging.sprintpcs.com to the 10-digit phone number, i.e.,
firstname.lastname@example.org. If the user has AT&T for his/her phone service, you can text the user by appending @txt.att.net to the number, e.g.
email@example.com. For T-Mobile, you can append @tmomail.net to the phone number.
When you are sending text messages from email, you need to keep in mind that SMS has a 160 character limit for messages sent in English. That limit applies because Mobile Application Part, which is a protocol within the Signalling System No. 7 (SS7) set of protocols is used for SMS messages. The data length is constrained by the number of bytes allocated according to the standard for that protocol; 140 bytes is the limit and, with 8 bits per byte, 140 bytes * 8 bits per byte = 1120 bits, so 1,120 bits are available for an SMS message, which equates to 160 characters if a character set is used made up of 7-bit characters, i.e., the GSM 7-bit alphabet, since 1,120 / 7 = 160. With 7-bit characters, you have 128 characters available for use since a bit can have only two values, zero or one, you have two raised to the seventh power, i.e. 27 = 128. If the 8-bit GSM 03.38 alphabet is used, instead, then you have 28 = 256 characters available. But the tradeoff is that the SMS message size is then only a maximum of 140 characters, rather than 160 characters, since 1,120 bits / 8 bits per character = 140 characters. And, if the 16-bit UTF-16 encoding is used, which is needed for some languages, then a user texting in one of those languages, such as Arabic, Chinese, Korean, Japanese, or Cyrillic alphabet languages, is restricted to a maximum of 70 characters, since 1,120 / 16 bits per character = 70 characters.
If a message exceeds the character limit, it may be truncated or converted
to a Multimedia Message Service (MMS) message, depending on the
provider. MMS is an extension to SMS that allows longer text messages, up to
40 seconds of video, an image or slideshow of images, or audio to be sent to a
recipient's phone. An MMS message is often referred to as a multimedia message,
a picture message, or a PXT. Many phone service providers provide a separate
fully qualified domain name (FQDN) to use for MMS messages.
E.g., Verizion uses
vzwpix.com, Sprint uses
pm.sprint.com, and AT&T uses
T-Mobile, on the other hand uses
tmomail.net for both SMS and MMS
messages. And T-Mobile's
Text and picture messaging
article notes "Messages are limited to 160 characters. If a message exceeds
160 characters, it's automatically converted to a picture message (MMS)." The
table below lists SMS and MMS domain names to use for various
carriers. To use the services, add "@" and the doman name after a
recipient's phone number, with no dashes or dots in the phone number, just the
10 digits of the phone number.
|Carrier||SMS gateway domain||MMS gateway domain|