You can write a personal letter and fax it to your senator/representative. I’ve faxed my congressperson and gotten a (mailed) letter in response. It bypasses the anthrax screening but perhaps carries a bit more weight than an email. I realize faxing is a sore point with some folks here, but you can use faxzero.com and it’s painless.
The OP is an imposter. The real Barack Obama would already know the answer, because he served as a senator.
It also depends on the content of the letter.
My Representative once showed a carefully hand-printed letter he received that went as follows:
That letter certainly got read by the Representative himself (and lots of others, too), but it didn’t have much influence on his vote!