import re
p = re.compile(r'^([^\s:]+):\s', re.MULTILINE)
test_str = "X-Apparently-To: test@yahoo.com; Thu, 09 Jun 2016 13:41:21 +0000 \nReturn-Path: \nReceived-SPF: pass (domain of yahoo.com designates 72.30.235.45 as permitted sender) \nReceived: from 127.0.0.1 (EHLO n3-vm9.bullet.mail.bf1.yahoo.com) (72.30.235.45) by mta1287.mail.ne1.yahoo.com with SMTPS; Thu, 09 Jun \n2016 13:41:21 +0000 \nDKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo-inc.com; s=yibm; t=1465479679; \nTo: test@yahoo.com \nFrom: \"Yahoo\" \nReply-To: \"Yahoo\" \nX-YMailISG: PCypxycWLDvGv4Bg8ShrtzVYi3vpFMAjYaqWyWybcVJ_ZQff eyquyqb..Qu6UKhX_Tyz5b3da2iDtRStJpVnNulZHOb8GznJQTCKk9sjvboS KsbzY4E1uScWz0Ieo0jjG0YHrB1dTCzOSeMiPNumCCFS1sR3_SkyMBGG_D2D wWtdRducxLa2YgEMMubVpMtNJMBv.bwk0.E.jQNEy8I3LnJEqcDpmIUM7bZL XgkEFz7yl1Zo6Sj4r0z6pGlVIFOql7uG9Bwq2VJoK1Q1upKJUOBfQqzf64y2 9fXLnQsWENpZloxwncGzLhdzEYGgE3xNuFV8QFxZGXyvtKZFoykH49M03URN jtx8Yg6ypjyRbBIRVJGVFbjAvW6io3yeyIFh042jlgYQtLxbneFA60hn9ifT Mit3bQ5l7Tginw0OgRM2cbqLo0tEZFt9vlN597Z3vPGwsVdBcTp9wnk6orj2 TqjEpAmODy3Yru2HzDP7Dbwq9CGaIozUm91VNWqw5Dy7AMQEsuvnBop7Fflk G21m1WKMBgrS.2bOLQ4797E09LjlyyoWI9FouUNNhDljnPPf2AeKUKzauctw ULOQPveWAm4lDsNLMp5yvXDYNIe5HMor84SVd8_xF3Icna1PAftXGzJUHrXK NZSEN_VO0GprGfaNQg4uSW_0wXFXwC6TYQ4CMjz53o0qNGpILogVfRLwFCFL DtW8nimkLLsNzmDajzJsR_juA86Orw2NE5ED4qdpPxmyxyrXYOQPu3O6zeYf 7mBzU0aX7VHJUxJ4L3HdB9qTjbTaCdnySrnjGtd7u9Cn9yRJirDNeg3UA82P PeA1ZDfc0vKdrn5QI6e6YKa2TTt7Dspy3jObgSapH5epc3LyQVyN7yjpxrq_ MXAbpqedjUfcwq3c7lpt8xxUxy.MXWg0fJO059xijvb_sYTaQTGUWAMeVU.6 IW.hSksejwpn._CgE9Kqabbk5qgYIdYRW1pmz5OBYh0skCX1TrFRuxbGvDit R_wr.wbTpJGiSST.b0ZetmgN72bVvlRtmNPw1Dk.zxaacXxhGSMWupPUDLJZ OMrap2ax8oiQrxT3jIhk8seIkaNJ.tGUhlPx6G4lJJaz0g89LmjBaEjGUG8P W3Phh9db3hjxUIX5UC0jg5ai2XZ7u_wXn2Muk61N1eRCZ0oA2S25YDPK1dh. 3VQ6pH8SSBxVkQHUJXbZUNqLAzi5V5wRS7oeitXERGgA2DiZB268.rJxS7di OMT5eGoITG4LnAo1M3nsVQ6xceHDd4v6KD9KfBgTHX_iLUv_skCv4dVUgVvj edKOFiOMHBTpJ9J9BECjTTzEUpc.fCNUcRwSsiSkqbRhUsAdCbxQZir3Nb1Z 6FzI6J2eNqpj4azjmDeI15R8MyN7VFc6bl6pCZySk2Tx5SQESDm.sVkADSVR pI2nuscEjU3xo_qGUxbh5mbAA17K2zYpcFXaOce8_9Eszos5pURCcdtBYUqI I_DOtvNe.zWY1ShRcr9ZzTj3ibmc7NBmvumhVMjqirb12mfJ6oxHv8d86gze HtAJmJghczUg5otSzdxSgEJJxjMZrzSidJ9FP.gPiPWtuukz82YpZ32MnCVs 6.V2DRxpUmZa31KH93QSEzwMlCn3FFTLBv9izcjoFP81yeAn.3QloF8XIC3K WmtXtloyeGjuygAhlkd_prXmMGGC5JmPlY8xu4k1NavkdDh6pG6zIkt83Wsd p.D.0BgM \nX-Originating-IP: [75.30.245.45] \nAuthentication-Results: mta1287.mail.ne1.yahoo.com from=yahoo-inc.com; domainkeys=neutral (no sig); from=yahoo-inc.com; dkim=pass (ok)"
print(p.findall(test_str))
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
['X-Apparently-To', 'Return-Path', 'Received-SPF', 'Received', 'DKIM-Signature', 'To', 'From', 'Reply-To', 'X-YMailISG', 'X-Originating-IP', 'Authentication-Results']