From: https://support.google.com/mail/troubleshooter/1668960?hl=en#ts=1665018,1665139,2769074

  Incoming Mail (IMAP) Server - Requires SSL
  imap.gmail.com
  Port: 993
  Requires SSL:Yes

  Outgoing Mail (SMTP) Server - Requires TLS
  smtp.gmail.com
  Port: 465 (SSL) or 587 (TLS)
  Requires SSL: Yes
  Requires authentication: Yes
  Use same settings as incoming mail server
  
  
  Full Name or Display Name: [your name]
  Account Name or User Name: your full Gmail address (username@gmail.com). Google Apps users, please enter username@your_domain.com
  Email address: your full Gmail address (username@gmail.com) Google Apps users, please enter username@your_domain.com
  Password: your Gmail password
  
  
  POP Settings: Server: ... pop.gmail.com Port: … 995 SSL: … Yes, you must use SSL (Google Apps policy)
  Username: … Your full e-mail address (include your login name and the @domain.whatever)
  Password: … Your normal e-mail password (assuming you reset it and it has already synced, as above)
  
  IMAP Settings: Server: …. imap.gmail.com Port: … 993 SSL: … Yes, you must use SSL (Google Apps policy)
  Username: … Your full e-mail address (include your login name and the @domain.whatever)
  Password: … Your normal e-mail password (assuming you reset it and it has already synced, as above)
  
  SMTP Settings: (I regardless of whether using POP or IMAP)
  Server: …. smtp.gmail.com Port: … 587 TLS or StartTLS: Yes, use TLS, you must use TLS (Google Apps policy)
  SMTPAuth: … Yes, you must authenticate to (SMTP) relay through Google Apps, see below
  Username: … Your full e-mail address (include your login name and the @domain.whatever)
  Password: … Your normal e-mail password 
  NOTE for SMTPAuth: For some e-mail clients/apps, there is a simple checkbox
  that allows using the “same settings as my incoming server”