[root@server log]# grep "customer@customerdomain.com" maillog*
maillog:Sep  6 22:44:16 server postfix/smtp[4849]: E63D72146DEC: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=5.6, delays=1/0/2.3/2.3, dsn=2.6.0, status=sent (250 2.6.0 <002701d3271e$ad64c180$082e4480$@mydomain.com> [InternalId=104535209021161, Hostname=BLUPR17MB0002.namprd17.prod.outlook.com] 25747 bytes in 0.334, 75.108 KB/sec Queued mail for delivery)
maillog:Sep  6 22:54:47 server postfix/qmgr[5930]: 39DD92146DE7: from=<customer@customerdomain.com>, size=30419, nrcpt=1 (queue active)
maillog-20170904:Sep  2 06:43:06 server postfix/smtp[13315]: 5496120CA8E2: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.74]:25, delay=3.8, delays=0.1/0/1.8/1.9, dsn=2.6.0, status=sent (250 2.6.0 <NDY5OTQZ.NTC2MTY5NA.6772509020634201707731201296@mydomain.com> [InternalId=104599633528047, Hostname=BY1PR17MB0006.namprd17.prod.outlook.com] 21373 bytes in 0.226, 92.176 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 07:54:25 server postfix/smtp[15818]: 0197F2090184: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.74]:25, delay=4.3, delays=0.11/0/2.4/1.8, dsn=2.6.0, status=sent (250 2.6.0 <NDQYOTKZ.NTY0OTC4MG.6702009020750201736735789593@mydomain.com> [InternalId=106072807310841, Hostname=CY1PR17MB0016.namprd17.prod.outlook.com] 21367 bytes in 0.328, 63.472 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 08:15:31 server postfix/smtp[16514]: B5D9D20CA8E8: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.181.42]:25, delay=3.7, delays=0.12/0/1.9/1.7, dsn=2.6.0, status=sent (250 2.6.0 <NDGWMDCY.MZYXOTAWNQ.6772409020810201742736996296@mydomain.com> [InternalId=105501576659315, Hostname=CO2PR17MB0011.namprd17.prod.outlook.com] 21412 bytes in 0.279, 74.876 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 08:19:00 server postfix/qmgr[5930]: 8ECF720CA912: from=<customer@customerdomain.com>, size=21747, nrcpt=1 (queue active)
maillog-20170904:Sep  2 08:57:41 server postfix/smtp[18126]: E37A42090184: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=4.3, delays=0.11/0/2/2.1, dsn=2.6.0, status=sent (250 2.6.0 <MTGYMDQ2.MZI2MJU0NW.6785609020850201751739405437@mydomain.com> [InternalId=105776454566965, Hostname=BY1PR17MB0007.namprd17.prod.outlook.com] 21296 bytes in 0.385, 54.011 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 09:25:41 server postfix/smtp[19135]: D9261215F2E3: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.181.42]:25, delay=4.7, delays=0.11/0/1.8/2.9, dsn=2.6.0, status=sent (250 2.6.0 <MZQXMJK0.NTE1NJIXMG.6777109020921201751741265343@mydomain.com> [InternalId=50908247360171, Hostname=BLUPR17MB0003.namprd17.prod.outlook.com] 20895 bytes in 0.710, 28.716 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 09:55:43 server postfix/smtp[20247]: 77099215F2E1: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=5, delays=0.11/0/2/2.9, dsn=2.6.0, status=sent (250 2.6.0 <MJG4ODUX.MZY3ODQ0NQ.6734009020950201753743006921@mydomain.com> [InternalId=50908247360713, Hostname=BLUPR17MB0003.namprd17.prod.outlook.com] 21383 bytes in 0.710, 29.403 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 10:36:47 server postfix/smtp[21951]: 5DB29215F317: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=4.2, delays=0.11/0/2/2.1, dsn=2.6.0, status=sent (250 2.6.0 <OTGZMDC2.NJGWNTQ2NW.6717409021030201758745411750@mydomain.com> [InternalId=104586748625434, Hostname=BLUPR17MB0004.namprd17.prod.outlook.com] 21232 bytes in 0.725, 28.568 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 10:57:45 server postfix/smtp[22602]: 52FA7215F2E5: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=4.8, delays=0.12/0/2.2/2.5, dsn=2.6.0, status=sent (250 2.6.0 <NTA3NJU2.MJUYMZC2MW.6710009021050201755746608671@mydomain.com> [InternalId=104616813397013, Hostname=BY1PR17MB0006.namprd17.prod.outlook.com] 20932 bytes in 0.377, 54.139 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 22:13:19 server postfix/smtp[46692]: 2959F215F2F2: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.74]:25, delay=3.9, delays=0.12/0/1.9/1.8, dsn=2.6.0, status=sent (250 2.6.0 <ODIZMTCZ.NJU2NZI0NG.6538309022205201719787012843@mydomain.com> [InternalId=104999065485664, Hostname=CY1PR17MB0014.namprd17.prod.outlook.com] 20242 bytes in 0.316, 62.424 KB/sec Queued mail for delivery)
maillog-20170904:Sep  2 23:19:10 server postfix/smtp[48773]: 5310F215F2EA: to=<customer@customerdomain.com>, relay=therapon-com.mail.protection.outlook.com[216.32.180.106]:25, delay=5.9, delays=0.12/0/2.6/3.1, dsn=2.6.0, status=sent (250 2.6.0 <NZC5MZQ0.MZUXNTA1NG.6546609022311201708790961921@mydomain.com> [InternalId=105840879075796, Hostname=BY1PR17MB0007.namprd17.prod.outlook.com] 20397 bytes in 0.985, 20.218 KB/sec Queued mail for delivery)

Sep  7 00:04:57 server postfix/smtp[7497]: 173E72146DE3: to=<customer2@customerdomain2.com>, relay=customerdomain2-com.mail.protection.outlook.com[216.32.181.42]:25, delay=8.2, delays=3.2/0/2.1/2.8, dsn=2.6.0, status=sent (250 2.6.0 <006901d32729$f229bb80$d67d3280$@axonadvisers.com> [InternalId=91517163143745, Hostname=BLUPR17MB0290.namprd17.prod.outlook.com] 33005 bytes in 0.465, 69.198 KB/sec Queued mail for delivery)
Sep  7 00:04:57 server postfix/qmgr[5930]: 173E72146DE3: removed