Why amazon emails goes to spam

Question

I have domain with 1&1 and my host is on AWS. I have configured my domain in Route5 and I set MX records. as per below:

10 mydomain.co.uk
10 mx01.1and1.co.uk
10 mx00.1and1.co.uk

The email transfer is working without any problem. The email are stored in 1&1 mail bucket.

I have an application that runs on Cakephp and here is my email Transport configuration.

'EmailTransport' => [
    'default' => [
        'className' => 'Cake\Mailer\Transport\MailTransport',
        /*
         * The following keys are used in SMTP transports:
         */
        'host' => 'email-smtp.eu-west-1.amazonaws.com',
        'port' => 465, // or 587
        'timeout' => 30,
        'username' => 'info@mydomain.co.uk',
        'password' => '*****',
        'client' => null,
        'tls' => true,
        'url' => env('EMAIL_TRANSPORT_DEFAULT_URL', null),
    ],

Now when I send emails the emails are sent to client account but the emails goes in spam. and I get red rock - email not encrypt.

Here is the example of the mail transfer from client account:

from:   Company Name Ltd <info@mydomain.co.uk>
to: Alex Manor <alex.manor@gmail.com>
date:   Jan 21, 2019, 11:13 PM
subject:    You have requested to reset password
security:    ec2-11-11-11-11.eu-west-1.compute.amazonaws.com did not encrypt this message Learn more

Answer 1

Thank to @Greg Schmidt.

'default' => [
        'className' => 'Cake\Mailer\Transport\SmtpTransport',  //<= The class name has to use SMTP
        'host' => 'smtp.ionos.co.uk',
        'port' => 587,
        'timeout' => 30,
        'username' => 'info@mydomain.co.uk',
        'password' => '*****',
        'client' => null,
        'tls' => true, 
        'url' => env('EMAIL_TRANSPORT_DEFAULT_URL', null),
    ],

After too much reading now I know you wouldn't need to change you host provider for email transport. As long as the email email transport methos is set correctly. you shouldn't get red lock.

Here is a good guide to configure the email DNS transfer

1. Log into 1and1 and go to Manage domains.
2. The domain was currently set to use 1&1 name servers with MX records of mx00.1and1.co.uk mx01.1and1.co.uk
3. Logged into Amazon Route 53.
4. Created a hosted zone for my domain.
5. Clicked Created record set then used the MX records from 1and1 ie, 0 mx00.1and1.co.uk and 1 mx01.1and1.co.uk - This was the important bit which ensured I didn't lose my inbound email
6. Went into SES and selected the option to use Route 53 which created my CNAME and TXT records automatically in Route53
7. As I had the 1and1 MX records set up in Route53 now, I could then go back to 1and1 and change the DNS settings to use other name servers, then entered my Amazon Route53 name servers instead.

Note: point #6 is good for who wants to use AWS host for email transport.