Limitations and features of the mail system

Limitations

1. The total size of an email, including headers, must not exceed 50 MB.
2. No more than 50 messages can be sent in 15 minutes from a single user.
3. When sending a message via the SMTP server, password authentication is required.
4. No more than 200 messages per day can be sent from technical domains *.nichost.ru.
5. No more than 50 recipients per message when sending via the web interface or the SMTP server mail.nic.ru.
6. No more than 25 recipients per message when sending from the hosting web server.
7. No more than 10 simultaneous connections from one IP address when sending messages.
8. No more than 7 simultaneous connections from one IP address when receiving messages.
9. No more than 7 connections to the webmail interface from a single IP address.
10. When using external mail (RPOP), no more than 3 remote accounts per user are allowed, and checks occur no more often than once every 15 minutes.
11. The session time for webmail access is 6 hours, but no more than 2 hours of inactivity.
12. Mass mailings must comply with item 10 of the “Hosting Service Regulationshttps://www.nic.ru/help/schedule-110-hosting-schedule_5966.html.”
13. Allowed characters in mailbox names: Latin letters “A…Z”, “a…z”, digits “0…9”, symbols “_”, “-”, and “.”. The name must start with a letter, cannot contain two consecutive periods (“.”), and must end with a letter, digit, or the symbols “-” or “_”.
14. Correct operation of mailboxes larger than 100 GB is not guaranteed.

Features

1. If a message delivery fails, subsequent attempts are made every 30 minutes for 3 hours, then every 2 hours for a week.
2. When delivering messages to a specific mailbox on the mail server, the flow of incoming messages must not exceed 30 messages per minute; if this limit is exceeded, the delivery queue for that mailbox is paused for 10 minutes.
3. No more than 20 Received headers are allowed (including those added by our server).
4. The mail system will reject messages if:

• The domain part of the return-path address is empty (missing);
• The domain part of the return-path address is given as an IP address;
• The domain part of the return-path address has neither MX nor A records in DNS;
• The domain part of the return-path address has an MX record that points to a non-existent A record;
• The sender’s domain in the “FROM” header is empty (missing) or contains a domain not added to the hosting service as a mail server name or its alias;
• The sender’s domain in the “MAIL FROM” envelope field is empty (missing) or contains a domain not added to the hosting service as a mail domain or its alias.

5. If the mail system cannot obtain DNS information for the domain in the return-path address, a temporary error is issued to the sender, and they must attempt to resend the message.
6. If the mailbox has reached its disk space limit, message reception is blocked until the issue is resolved; the sender receives a temporary error and must try to resend the message.
7. Messages sent to a mail group will not be delivered to subscribers on external addresses if:

• The group is created on a service domain of the form *.nichost.ru;
• MX records for the domain do not point to hosting servers.

8. On mail domains, a postmaster mailbox is created for technical messages; forwarding for this mailbox is enabled to the addresses listed as contacts in the hosting agreement.
9. Forwarding to external addresses is not performed for messages recognized as spam, messages with an empty “MAIL FROM” envelope field, and delivery reports.
10. Features for working with internationalized domain names (IDN):

• The username in an email address must be in Latin characters, e.g., info@ник.рф;
• When configuring and using email, issues may arise due to lack of support for such domains in third-party services and mail clients. Rucenter services fully support working with IDNs;
• When configuring software, it is recommended to use the domain name in punycode format for correct operation.