No secrets here, these are basics. Since your mail is mostly transactional your volume is significantly low compared to people who specialize in mailing. Transactional email is less likely to produce spam complaints. Misspelled addresses are detected on first sends, which is what you want. You're going to get an error at the smtp level or a bounce.

Here's a secret - Monitor the ip to domain ratios , usually gmail will allow 1k of mail from the same ip per hour.