Please add the following DNS records at Namecheap control panel:
Type: MX
Name: @
Mail server: mx1.hostinger.com
TTL: auto
Priority: 5
Type: MX
Name: @
Mail server: mx2.hostinger.com
TTL: auto
Priority: 10
Furthermore, to help with outgoing email deliverability, you will also need to add the following SPF and DKIM records:
Type: TXT
Name: @
Value: v=spf1 include:_spf.mail.hostinger.com ~all
TTL: Default value
Type: CNAME
Name: hostingermail-a._domainkey
Target: hostingermail-a.dkim.mail.hostinger.com
TTL: 300 seconds
Type: CNAME
Name: hostingermail-b._domainkey
Target: hostingermail-b.dkim.mail.hostinger.com
TTL: 300 seconds
Type: CNAME
Name: hostingermail-c._domainkey
Target: hostingermail-c.dkim.mail.hostinger.com
TTL: 300 seconds
{"html5":"htmlmixed","css":"css","javascript":"javascript","php":"php","python":"python","ruby":"ruby","lua":"text\/x-lua","bash":"text\/x-sh","go":"go","c":"text\/x-csrc","cpp":"text\/x-c++src","diff":"diff","latex":"stex","sql":"sql","xml":"xml","apl":"apl","asterisk":"asterisk","c_loadrunner":"text\/x-csrc","c_mac":"text\/x-csrc","coffeescript":"text\/x-coffeescript","csharp":"text\/x-csharp","d":"d","ecmascript":"javascript","erlang":"erlang","groovy":"text\/x-groovy","haskell":"text\/x-haskell","haxe":"text\/x-haxe","html4strict":"htmlmixed","java":"text\/x-java","java5":"text\/x-java","jquery":"javascript","mirc":"mirc","mysql":"sql","ocaml":"text\/x-ocaml","pascal":"text\/x-pascal","perl":"perl","perl6":"perl","plsql":"sql","properties":"text\/x-properties","q":"text\/x-q","scala":"scala","scheme":"text\/x-scheme","tcl":"text\/x-tcl","vb":"text\/x-vb","verilog":"text\/x-verilog","yaml":"text\/x-yaml","z80":"text\/x-z80"}