through a spam blocker

[WrigleyF]

Do you have any broad tips for making sure your emails don't get stopped by a spam blocker? I've sent non-spam emails to people I know, only to get an error message mentioning spam.

[greenmatter]

different spam filters have different red flags to qualify an email as spam. if the receipient is receiving the email for the first time then there is a chance it will be flagged unless you are in their white list or contact list. I will follow up important first emails with a phone call just to make sure they received it.

[suwunk]

Certain criteria get more points than others. Here’s a sample of criteria from Spam Assassin:

Talks about lots of money (.193 points)
Describes some sort of breakthrough (.232 points)
Looks like mortgage pitch (.297 points)
Contains urgent matter (.288 points)
Money back guarantee (2.051 points)

If your campaign’s total “spam score” exceeds a certain threshold, then your email goes to the junk folder. You’re probably thinking, “What’s the threshold I need to stay under?” Sorry, but the number is different for every server.
How To Avoid Spam Filters | MailChimp

[peleus]

I think no one can really control this since standards update almost regularly. Just make sure to add the sender's email every time the blocker tag it as spam to the trust list.