What are some good solutions for sending verification code emails?

The user Passport system, registration, and password retrieval all send verification codes through email. Is there any good solution to achieve this?
I used a private QQ mailbox before. I found that occasionally the system would send me an email asking me to enter a verification code, and I was afraid that if I used it too much, I would be blocked by Tencent or automatically moved to the trash can.
Also, under what circumstances do I need to use a queue to send emails?

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The user Passport system, registration, and password retrieval all send verification codes through email. Is there any good solution to achieve this?
I used a private QQ mailbox before. I found that occasionally the system would send me an email asking me to enter a verification code, and I was afraid that if I used it too much, I would be blocked by Tencent or automatically moved to the trash can.
Also, under what circumstances do I need to use a queue to send emails?

The following situations require the use of email queues:
1. When sending emails in batches to multiple users, the queue must be called asynchronously, because after clicking send, the operator may close the page. At this time, only sending emails asynchronously in the background will not work. As for missing emails.
2. Register, log in, and retrieve your password. You can use the SMS platform verification code or the email service area.

If you send a large amount of emails, you usually need to purchase specialized services.

As for using queues, sending emails is a time-consuming operation, and asynchronous implementation is better.

I have used Alibaba’s free corporate email, and it’s no problem sending to 126, QQ and Gmail in China.
Occasionally other email addresses may appear in "Spam".

When using asynchronous implementation, you will generally consider using a message queue. You can consider django celery + RabbitMQ

You can try these things

1. SendGrid

2. MailGun

3. SendCloud