Contacts re email deliverability problem to tmomail.net?

Hi, folks, A client of mine is having trouble delivering (legitimate) email to tmomail.net, and I'm having trouble finding the right contact. (e.g. postmaster bounced). I've verified the legitimate nature of the email (only user-initiated, and nothing more), the valid SPF, A, PTR, and MX records, etc. We're also having no trouble sending the equivalent messages to the email-to-SMS gateways at ATT Wireless, Verizon Wireless, Sprint, etc. Any suggestions for the best points of contact at T-Mobile USA (tmomail.net)? thanks! Graham Freeman graham.freeman@cernio.com (Email/Jabber/SIP) +1 415 462 2991 (office)