Try sending an email to VZW's MMS gateway. MMS has longer character limits per message than SMS. If your recipient is receiving long messages from other customers, I'm guessing he or she is receiving the message as a MMS (aka picture message) rather than SMS (aka simple text message) Depending the the recient's account (some accounts on some carriers, *cough*ATT*Cough) can't receive MMS from the email gateway unless the user is set up to receive mms from the gateway.
Try sending the long message as an email to Verizon:
. Failing that you could try Verizon:
, but that's the one for plain text messages.
The use the email gateways all of the time since I have unlimited data, and sending SMS or MMS as data is free for me. The recipient and read and replay as a SMS or MMS, yet it's received back as an email for me, so it's low cost fo both of us! Cha-ching!