Cell Carrier Email Domain
AT&T Enterprise Paging page.att.net
AT&T Wireless txt.att.net
Alaska Communication Systems msg.acsalaska.com
Alltel  text.wireless.alltel.com
Now part of AT&T
Australia T-Mobile/Optus Zoo (Optus)
Appears they charge for the service
Bell Mobility & Solo Mobile txt.bell.ca
Bluegrass Cellular sms.bluecell.com
Boost Mobile myboostmobile.com
Cellcom cellcom.quiktxt.com
Cellular South (C Spire)
(now cspire1.com)
Centennial Wireless cwemail.com
Chatr pcs.rogers.com
Cincinnati Bell gocbw.com
Cingular cingular.com
Merged with AT&T Mobility 2007
Cingular Prepaid cingulartext.com
Cox Wireless Discontinued 2012
Cricket Wireless mms.cricketwireless.net
Digicel St. Lucia digitextlc.com
Fido fido.ca
Google Voice Not an actual carrier
GCI Alask Digitel (GCI) mobile.gci.net
IV Cellular (Illinois Valley Cellular)
i wireless (iWireless) iwspcs.net (T-Mobile)
iwirelesshometext.com (Sprint PCS)
Koodo Mobile msg.telus.com
Lime txt2lime.com
Metro PCS mymetropcs.com
MTS Mobility text.mtsmobility.com
NET10 Determine NET10's carrier
Nex-Tech sms.nextechwireless.com
nTelos pcs.ntelos.com
Will change to Sprint early 2016
O2 (M-mail) mmail.co.uk
O2 Powered Networks  
O2 UK o2imail.co.uk
Optus optusmobile.com.au
Appears they charge for the service
Orange orange.net
PC Telecom mobiletxt.ca
PTel Mobile tmomail.net
Pioneer Cellular zsend.com
Pocket Wireless sms.pocket.com
Republic Wireless text.republicwireless.com
Rogers Wireless pcs.rogers.com
SaskTel sms.sasktel.com
Sprint messaging.sprintpcs.com
Straight Talk Determine Straight Talk's carrier
Syringa Wireless rinasms.com
T-Mobile tmomail.net
T-Mobile UK t-mobile.uk.net
Telstra onlinesms.telstra.com
Telus Mobility msg.telus.com
Three three.co.uk
Tracfone Determine Tracfone's carrier
US Cellular email.uscc.net
Unicel utext.com
Verizon vtext.com
Viaero viaerosms.com
Virgin Mobile vmobl.com
Virgin Mobile Canada vmobile.ca
Virgin Mobile UK vxtras.com
Vodafone No email-to-SMS service
Wind Mobile txt.windmobile.ca

See Also
SMS cell carrier not listed