blza? Eu sugiro usar um serviço de email como o da SendGrid (https://sendgrid.com/docs/api-reference/).
Estou usando nas minhas aplicações e é show de bola!
Eles tem até um pacote pronto para node.js (https://github.com/sendgrid/sendgrid-nodejs)
Uma das vantagens é poder acompanhar pelo dashboard se o email foi entregue, se foi lido, e em caso de erro vc tem como rastrear
Abraços!
This is the mail system at host UBMSA01.spo2.umbler. com.
I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
brunobuzios@hotmail.com: host aspamout01.umbler.com[187.84.237.181] said: 554
5.7.1 You can not send a message because your domain has been penalized for
spam, or either does not have the MX and SPF records configured. For help,
please quote incident ID 073RbXHeC. (in reply to end of DATA command)