SharePoint document library Incoming email with external email provider such as nameCheap

How to enable SharePoint document library for Incoming email from other email provider (namecheap).

I already configured SMTP . where I Setup all the required parameter. But I only found parameter for outgoing email. After setup my out going emails are working fine.

for incoming, I setup in CA incoming email settings , for Document library enable the incoming the emails & other settings.

Incoming emails is not working , Not sure where I will setup pop3 and imap settings for incoming emails . I do not have exchange setup , My emails are hosted at name cheap.