In theory you would want
strTo = ActiveCell.Offset(0, -29).value & ", " & ActiveCell.Offset(0, -28).value & ", " & ActiveCell.Offset(0, -27).value
strCc = ""
strBcc = ""
but you may have trouble with Outlook not validating that as a suitable address. Better to leave the strings as they are and add them to the message separately as recipients e.g.
With olMail
.Recipients.Add(strTo).Type = 1
.Recipients.Add(strCC).Type = 1
.Recipients.Add(strBcc).Type = 1
.display
End With
You don't then need .To, .CC or .BCC values.
If you want to hide the recipient details from the other two recipients set .Type = 3 instead of 1 and then they will all go as BCC.