[BUG] Emails from SendGrid are being blocked by hotmail accounts.

**Describe the bug**

When the system for DERT2025 is trying to send emails we send them from the account of the Event organisers to the email addresses on the groups. When the email address on the groups is a .hotmail.co.uk address Hotmail is refusing to accept the emails.

It appears to be a common issue. THis bug is raised to look for a better alterative in order to gain effective delivery regardlesss of the reciepient.

Considered option include:
- Use common email such as dertinfo email where we can validate the domain. (However this will likely result in groups contacting DertInfo & not the organisers)
- Change provider for email (However this may have the same problem)

Other options to be cosnidered

**To Reproduce**
Steps to reproduce the behavior:
1. Create event with organisers email address
2. Crete a group with a *@hotmail.co.uk email address
3. REgister for the event with the group
4. Registration emails are not received by the group after multiple reties at send grid

**Expected behavior**
Hotmail does not block the email.

**Screenshots**



**Desktop (please complete the following information):**
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**Smartphone (please complete the following information):**
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**Additional context**
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