You should explain that you don't believe he gave the required 30-day notice of the rent increase based on the postmark on your letter. Acknowledge that you received the notice and that you will pay the increased amount beginning November 1. In addition, I'd let the landlord know whether you'd like to sign a new lease. As you experienced renters know, this is a common rental increase tactic. Many landlords reduce the rent increase if the tenant will commit to a term lease of 6 months or more.
Some landlords offer even greater reductions for a commitment to a term lease of one year.
Well, it doesn't hurt to ask, especially if you're a good tenant. Sometimes, the landlord may not want to lose you as a tenant, especially in a smaller complex. A landlord has to weigh the possibility of increased income from a new tenant willing to pay the higher rent against the possibility they'll be a less desirable tenant than you. The extra income might not be worth it to them. Of course, a little persuasion never hurts either.