Office 365/Exchange Problem: Access Denied, Bad Sender


New Member
I'm getting marked as spam by Office 365/Microsoft Exchange.

My domain for sending emails is provided by Comcast: For lack of technical proficiency, I'll say that Comcast uses the 365/Exchange platform to service the domains.

Here is how I connect:
SMTP-Host: -> TLS v1 Exp
Authent.: ESMTP -> Login
One Connection, Single Delivery
I'm sending out 5 every minute or so . . . a rate of 275/hour, well under the published limit.
After about 90 emails, they shut me down.
550 5.1.8 Access denied, banned sender
Then I have to log into the admin panel and unblock the account and then wait for the unblock to populate on the servers.

The frontline tech support folks at MS can't pinpoint a reason why this is happening.

One thing I've discovered: if I send 80 emails (5/minute) and then wait a little while, and then fire it up again for another 80 or so emails, I'm not getting the problem. Insert sad-faced emoji here, not much of a work around.

Possible Triggers?
I'm not a Mac. MS may hate me because I'm on a Mac?
The email I send out has two links to static web pages and one link to a personalized URL. The personalized URL is on a Lasso database server.
On the support page for MBM and Office 365, I think it asked for a port 587 and deliveries of 25 every 3:45. That got me kicked out even faster. My log says I'm using port 25.

I'm out of ideas. Any help would be greatly appreciated.


New Member
What Microsoft is telling me: It's not an issue of the amount or number of emails I'm sending on an hourly or daily basis. They have software that is sniffing it out as "solicitation" and unless I can "justify" my solicitation, they're not sure they can help me out.

Stay tuned . . .

In the meantime, if anyone has suggestions for a reliable email server with good customer service and a willingness to cater to legitimate bulk email senders, I'm all ears.

Not interested in Constant Reject or Mail Chump, thank you.