ss = ['test2@gmail.com:123456',
'test2@hotmail.com:124554134',
'test1@yahoo.com:fdsfsdfe',
'test5@gmail.com:9875464',
'no com']
res = [s.rsplit("com:")[1] if "com:" in s else s for s in ss]
print(res)
c3MgPSBbJ3Rlc3QyQGdtYWlsLmNvbToxMjM0NTYnLAondGVzdDJAaG90bWFpbC5jb206MTI0NTU0MTM0JywKJ3Rlc3QxQHlhaG9vLmNvbTpmZHNmc2RmZScsCid0ZXN0NUBnbWFpbC5jb206OTg3NTQ2NCcsCidubyBjb20nXQpyZXMgPSBbcy5yc3BsaXQoImNvbToiKVsxXSAgaWYgImNvbToiIGluIHMgZWxzZSBzIGZvciBzIGluIHNzXQpwcmludChyZXMp