注册并使用用户的电子邮件域

Question

In my current application i want to add a new feature that customers will be able to register their own email domain server if they have any. Currently i am sending all emails using my own application domain.

I want to know how we can accomplish that using ASP.NET WebApi & C# that user will allow to validate and register their own email domains instead of using the default one.

Do we need user's DKIM and SPF records ?

Answer 1

If the user provides the credentials to their own email service

Then you don't need to look at DKIM and SPF records. The user should do that himself.

You will have to collect from the user:

• email service type (smtp, mandrill, postmarkapp...)
• email service host name (if smtp)
• credentials or api key
• and maybe service-specific options

If you use your own service to send emails

Then the user will have to add a DKIM entry and update the SPF entry on their domain name. You will have to provide the values to your user depending on your email service.

You can take inspiration from all those services that allow the same kind of feature ( mailchimp , mandrill , postmarkapp , zoho ...).

Check for DNS email records

In both cases, you can use a DNS client to verify the DNS records are OK. You will be able to tell the user whether records are missing.

Here a sample code to start checking the SPF record with ARSoft.Tools.Net .

var client = new DnsClient(servers, 10000);
var spfRecords = client.Resolve(item.Name, RecordType.Txt);
if (result.AnswerRecords == null || result.AnswerRecords.Count == 0 || result.ReturnCode == ReturnCode.NxDomain)
{
    // spf record is missing
}
else if (result.AnswerRecords.Count == 1)
{
    // check the record value with SpfRecord.TryParse(item.ActualValue, out spf)
}
else
{
    // too many spf records
}