Ted's district is the whole state of Texas. I'm in Texas too, but I've never sent Ted an email or a letter to his Senate address, so I can't vouch for the auto-reply.
Ted has disappointed me with some of his votes lately, but that said, the man is in the high 90 percentile range as a conservative, and still has my support. At this point, though, I'm supporting him for Trump's eventual VP - not for president.
Remove Trump from the equation and Ted can't win this by himself. He needs to become more well established in office, and demonstrate real leadership over time, before he'll be able to win a presidential election alone.
I have called one of Cruz’s offices in Texas asking for information about bills and interpretation of laws. Staff person said they would call me back and within two to three days they did and had the information I asked for. Staffer also asked me if I needed him to email me the reference sources so I could look them up and copy the info for my use. Great staff.
I have sent Cornyn a number of emails over the years voicing my opinion on many issues. Always get an email response but I have yet to have one which dealt with the issue contained in my email to him.