Score:0

Using mail as the subdomain for webmail?

cn flag

I recently purchased a domain and I am planning to use the subdomain smtp.example.com for my mail server and mail.example.com to host my webmail app. Could there be any issues with using mail for something other than a mail server?

djdomi avatar
za flag
end-user question should be asked on Superuser.com
Score:2
cn flag

No.

Subdomains follow the usual domain requirements:

Use only these characters:

  • a-z (case-insensitive)
  • 0-9
  • - (not as a starting or ending character)

Label must 63 characters ("octets") or less and names must be 255 characters ("octets") or less.

For more information, see RFC 1035.

Score:1
kr flag

Can't think of any problems besides mixing them up yourself. Why not run both webmail app and smtp service using the same hostname?

Score:1
es flag

No issues. Remember, it's always DNS! Meaning, you control what the outside world sees as your mail server through the use of MX records in DNS. When another server is sending an email along that's addressed to [email protected], the outside DNS server will lookup your MX record in your root domain example.com and find whatever you put in there as the MX record, in this case smtp.example.com, then it will initiate a connection to whatever IP address you identify in DNS as smtp.exmaple.com. If you want webmail setup on mail.example.com for your users, then that's also fine.

As was mentioned already, depending on your setup, you could just have one name for both like mail.example.com. In the example of using Microsoft exchange, OWA/Webmail usually listens on port 443. SMTP traffic default listens on port 25 and sometimes port 587. So when a user opens a browser and punches in mail.exchange.com, it will default to use HTTPS over 443 and your server will answer that connection with the webmail website. If an outside email server wants to send someone in your domain an email, that server will reach out to mail.example.com over port 25. Since the connection is coming into your server on port 25, your email server knows that this is SMTP traffic and will accept and route the email to your users.

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