Office 365 SMTP Emails Getting Blocked

[Auguy]

I have a.Net program to send Office 365 Emails.
We sent about 15 in a two minute period the other day and most got blocked.
I'm sure we're not exceeding 30 per minute.
Using two different accounts as the From and Reply To.
Seems when we send to the same recipient more that once in a row they are getting blocked.
Is this some sort of timing issue?
Some other restriction?
Just sent a test email and it went thru, but didn't try more than one in a row
I'm using different accounts for the send from and the reply to.

Is this another misleading error from MS and it really means the recipient has to whitelist our from address?

Here is a sample Office 365 Error

Your message couldn't be delivered because you weren't recognized as a valid sender. The most common reason for this is that your email address is suspected of sending spam and it's no longer allowed to send email. Contact your email admin for assistance.
Diagnostic information for administrators:
Generating server: BYAPR05MB6440.namprd05.prod.outlook.com
bobsmith@gmail.com
Remote Server returned '550 5.1.8 Access denied, bad outbound sender AS(42004)'



Auguy
Sylvania/Toledo Ohio

 

[Andrzejek]

>I'm sure we're not exceeding 30 per minute.
Is that your Company's policy?

I had similar issue and it was caused by sending too many e-mails in a short time from my app. Our e-mail servers (by our policy) detected that as 'not allowed'. After talking to our Admin and explaining the reason of sending multiple e-mails at one time, my application was excluded from that rule and I can send all what I need.

---- Andy

"Hmm...they have the internet on computers now"--Homer Simpson

 

[strongm]

Possibly

https://docs.microsoft.com/en-us/mi...d-users-portal-after-spam?view=o365-worldwide

 

[Auguy]

Andy, I found the 30 per minute rule somewhere online when researching this issue.

Strongm, Thanks I've seen that but will review again.

My concern is will this happen again once it's unblocked due to the way I'm sending the emails.

Auguy
Sylvania/Toledo Ohio

 

[Auguy]

Follow up.
Does anybody have any alternatives to using Office 365 to send emails with attached invoice PDF files from a program?
This office uses 365 for their normal emails, that's why I was going to use it.
We would probably send 100-200 every couple of days.
Trying to avoid these emails being marked as spam.


Auguy
Sylvania/Toledo Ohio

 

[Andrzejek]

I have a code in VB6 using MicroSoft CDO for Windows 2000 Library as a Reference to send e-mails that works for last many years...
Yours if you want to 'translate' it to VB.NET

---- Andy

"Hmm...they have the internet on computers now"--Homer Simpson

 

[Auguy]

That would be great, thanks.
Can you post a link or code?
I don't have any problems sending the SMTP emails, it's just that 365 is marking them as spam and blocks the account.
Looking at MailKit, but think it might do the same thing.


Auguy
Sylvania/Toledo Ohio

 

[Andrzejek]

There you go: thread222-1650646

You will need your cdoSMTPServer address:[tt]
...
.Item(CDO.cdoSMTPServer) = "[red]NTSMTP.ABC.XYZ.LAN[/red]"
...[/tt]

---- Andy

"Hmm...they have the internet on computers now"--Homer Simpson

 

[strongm]

Not sure that'll help as this solution will still be relaying through the server that is blocking the mail ... You'd need to work as your own email gateway instead.

 

[Auguy]

Thanks,looking at gmail as an option with Google Workplace.
And a paid service like SocketLabs

Auguy
Sylvania/Toledo Ohio