INDYMAC HOME EQUITY MORTGAGE LOAN ASSET-BACKED TRUST, SERIES 2006-H2 $486,654,000 INDYMAC HOME EQUITY MORTGAGE LOAN ASSET-BACKED NOTES, SERIES 2006-H2 INDYMAC MBS, INC. (DEPOSITOR) INDYMAC BANK, F.S.B. (SPONSOR/SELLER) UNDERWRITING AGREEMENT June 26, 2006