We are using Sendgrid account which is hosted in Microsoft Azure,
We are facing issue while sending mails to Mailsac, the mails are in Deferredstate and not getting delivered please find the screenshot for your reference,
Error message is : Email was deferred due to the following reason(s): [IPs were throttled by recipient server]
Emails may be throttled based on recipient address, sender address / domain, IP address etc. Since you are sending to a non-private domain and non-private address, your emails are being throttled.
Our paid plans (https://mailsac.com/pricing) offer much higher throttling limits. The paid plans come with a many other features such as private domains, higher api limits, email support, and vendor risk assessment support.
This forum post touches on several of the aspects of throttling How Many Emails Can I Send in a Day