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Hi, my first broadcast in mailwizz got very few bounces but the second and third started bouncing Gmail address’s. Now every gmail is getting bounced with this message:

Our system has detected that this message is 550-5.7.1 likely suspicious due to the very low reputation of the sending 550-5.7.1 domain. To best protect our users from spam, the message has been 550-5.7.1 blocked. Please visit 550 5.7.1

is there any fix for this problem at all?
This has been brought up several times here in the forums, but I also know that the search feature here is limited, so try this search in Google instead: "550-5.7.1"

I guess the answer is to use a better delivery server. Is it blacklisted?
Go here, and check your sending reputation score, anything below 50 is generally bad news, reputation here should ideally be at least 80 plus

Also go here and check your blacklisting

Also let me know if you want a free copy of the mailwizz server reputation monitor extension, link below on details :

which does the above stuff for you automatically, letting you know when your delivery server(s) are compromised on reputation.
Did you check domain and ip blacklisting ?

"very low reputation of the sending 550-5.7.1 domain" is the focus point of the return error.

senderscore obviously doesn't show internal metrics of individual esp's and they can and do all rate differently.

Also send a test to to see if your email content is listed on razor.

Otherwise to many people have hit the spam button at gmail on your mails, usually not using the server for a few days can help.

Try spin text, or dynamic content when sending so each email is differentiated from each other email, this usually overcomes razor and in fact makes sure you don't get listed there

If its only gmail that's an issue, and if you can live with going to the promotions folder, sendgrid will basically guarantee delivery there regardless of your general domain reputation etc. So you can send to everyone else as per normal, and use sendgrid for gmail only until things clear up on your usual delivery server.
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I checked both ip and domain, mail tester got a 10 out of 10. I have only been sending to a small list of under 3k which are my clickers from the last 2 weeks from my Aweber. And only sending at 1 email a minute.
Under those conditions it does seem very odd that gmail would be blocking you, perhaps try a different email format/content, perhaps yours is triggering something similar they've seen.before.

Its usually quite easy to diagnose and make adjustments as needed, just a few tests required to see what the trigger cause is.

I've sent over 200,000 cold emails at a go to various email destinations, and a lot were gmail accounts. At the time gmail weren't overly happy with me but I never hit the blocking stage but now from those same servers my emails go to the inbox with no infrastructure changes at all, although I have tamed the volumes down a bit.

A couple of local banks still don't like me sending to their employees but that's about the only issues I've encountered, and banks do have higher standards of security anyway.