Cheap email backend for small Django app

I'm looking for suggestions on which email backend to use for a small django application.

Will use for account verification after registration and probably in the future, for user updates.

Right now, I know about SendGrid, Anymail, and MailGun. I have used SendGrid and MailGun in the past, but is there some alternatives for a cheaper option?

It would be nice if they had a django email backend support for easy integration.

Edit: SendGrid and MailGun have a free tier of 100 emails per day.

I also heard about using Gmail. Does anyone have experience using it?

Edit 2: Since my application might be able to go with just having a limit of < 100 emails per day. I decided just to go with MailGun, and if there will ever be more, Zoho's Zeptomail and AWS SES are one of the cheapest, I guess.

Appreciate all of your responses and suggestions guys!

TIA.