Although I have already done everything, like adding SFP, DKIM and sending plain text in my emails, I want to notify Gmail, Hotmail, Yahoo, and other "big" popular email providers that I'm legitimate. How and where do you do that?
If you are doing everything right, you should have few problems. The more things you do right the more likely you won't get flagged as spam. There are a few sites that will evaluate your mail server to verify your configuration is correct.
I have noticed a lot of automated systems don't use their FQDN in their HELO command. This makes you appear more like a spammer. Checking your server with port25 and intoDNS to verify your configuration helps.
Some of the big sites have a page where you can register your mail server. You may also want to register with
dnswl.org which provides a reliable whitelist of legitimate senders.
EDIT: I have documented my experience with Detecting Email Server Forgery. The article also has a fair bit of information on avoiding being seen as forging an identity and verifying a servers configuration.
You can't do that, you can only play by the rules and hope for the best. You are only as legitimate as your administration techniques over time demonstrate you to be.
Some things you can do to get started are have your users to add you to their address books and don't break any usage policies or industry accepted behavior guidelines. If an individual provider tags you as being bad, they usually have a process you can go through to get untagged, but it varies by provider.
If you are already following best practices then you shouldn't have too many issues, unless you are sending really high volumes. The major providers all have spam filters which adapt to what they view as normal traffic, so the problems only really happen when mailing from new (previously unused) IP addresses.
I'm not about to go over all the mail best practices here, there are plenty of sites doing that already.
- Hotmail have an SPF / SenderID register, which you can enrol in.
- Yahoo have a bulk mailer sender form, which lets you submit your IP addresses for analysis. It's not whitelisting, but apparently gives you preferential treatment.
- You should register for the spam feedback loops of major providers, and use the reports to unsubscribe users from your lists:
- Take a look at Hotmail/Live's SNDS. It gives you visibility into bounce and complaint rates across the IP addresses you send mail from.
- Keep an eye on how mail providers are handling your mail. If they are getting deferred, they are rejecting them, or they are going into the bulk/spam folder then you can raise a support ticket:
Many of mail servers uses Spamhaus. There is a proper procedure to remove your IP from Blocklist.