Cant send emails to outlook and hotmail

There are a group of email addresses that we cant send emails to hotmaiil, live, outlook related domains.

Using sendgrid

They send emails to gmail fine

But cant send to the hotmail related ones.

550 X.X.1 Unfortunately, messages from [X.Z.X.Z] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [VI1EUR04FT062.eop-eur04.prod.protection.outlook.com]X

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Contacted them they say issue with IP being used by spammer in shared ip pool etc...

But we need to get emails to these users for signup, less than 50 per day per stil...

ive got an option of using a different provider just for these emails or php mail()

are these good smtp providers with API we can use. Ive heard of elasticemail but i think they dont do a free plan anymore

Why dont you just buy a dedicated IP from sendgrid?

costs a lot

Getting a new IP won't solve it. MSN/Outlook/Hotmail has a reputation of blocking any emails from any small-time sender. We had the same issue, and it took our upstream to get this sorted. In total, it took about a month for them to get back to us. Just don't give up, and ask your hosting co to help.

Contact Sendgrid about this issue, they might be able to work around it..

move to amazon ses services you can easily integrate it with PHP smtp, hotmail and related all Microsoft domains are pretty hard to deliver they are very strict about IP reputation, if its just 50 emails a day maybe u can add one gmail as well for sending with PHP smtp classes

sendinblue.com better than sendgrid. My mails always go spam folder. I using sendinblue now. All mails in inbox.

The only solution I found is to pay SendGrid for my own unique and clean IP. Still, the emails being sent to hotmail addresses are often put into the spam box.
Better you can write to SendGrid solved. maybe it will be help for you https://sendgrid.com/blog/a-few-more-things-you-can-do-to-get-delivered-hotmail/