What is the difference between Notify and building my own email delivery stack?

If by Notify you mean a managed notification/email service (for example, a GOV.UK-style email notification platform), the difference is mostly:

Notify

A managed service where you:

• send emails through an API
• use prebuilt email templates
• get delivery tracking, retries, bounce handling, and analytics
• don’t manage SMTP servers, IP warmup, deliverability tuning, or scaling

Pros

• Fast to integrate
• Less maintenance
• Better deliverability out of the box
• Usually cheaper and simpler for small/medium volumes
• Compliance/security features are handled for you

Cons

• Less flexibility
• Ongoing vendor dependency
• Pricing can become significant at high volume
• You’re limited to the provider’s features and policies

Building your own email delivery stack

You set up everything yourself, typically including:

• SMTP/MTA infrastructure
• DNS records (SPF, DKIM, DMARC, reverse DNS)
• bounce processing
• queueing and retries
• suppression lists
• tracking and analytics
• IP reputation management and warm-up
• compliance and abuse handling

Pros

• Full control and customization
• Can be cost-effective at very large scale
• Easier to meet unusual infrastructure/compliance requirements
• No dependency on a third-party service for sending logic

Cons

• High engineering and operational overhead
• Deliverability is hard to get right
• Requires ongoing monitoring and maintenance
• Risk of spam filtering, blacklisting, outages, and slow scaling
• More time to build and keep reliable

Rule of thumb

• Use Notify if you want to send emails reliably without building email infrastructure.
• Build your own stack only if you need deep control, have large scale, or have strict technical/compliance requirements.

If you want, I can also compare them on cost, deliverability, or implementation effort.