Sử dụng Exchange Remote Connectivity Analyzer (trong EMC Toolbox) + Tool để kiểm tra kết nối

Performing Outbound SMTP Test
 The outbound SMTP test failed.
 Test Steps
 Attempting reverse DNS lookup for IP address xxx.xxx.xxx.xxx.
 Reverse DNS lookup failed.
 Additional Details
 A Winsock error occurred while trying to resolve the host. Error: 11004

Performing Real-Time Blackhole List (RBL) Test
 Your IP address wasn't found on any of the block lists selected.
 Test Steps
 Checking Block List "SpamHaus Block List (SBL)"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "SpamHaus Exploits Block List (XBL)"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "SpamHaus Policy Block List (PBL)"
 The address isn't on the block list.
 Additional Details
 IP addressxxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "SpamCop Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "NJABL.ORG Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "SORBS Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "MSRBL Combined Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "UCEPROTECT Level 1 Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Checking Block List "AHBL Block List"
 The address isn't on the block list.
 Additional Details
 IP address xxx.xxx.xxx.xxx wasn't found on RBL.

Performing Sender ID validation.
 Sender ID validation was performed successfully.
 Test Steps
 Attempting to find the SPF record using a DNS TEXT record query.
 ExRCA wasn't able to find the SPF record.
 Additional Details
 No records were found.

Ghi chú:
+ ISP này (FPT) block SMTP outgoing on port 25
+ DNS domain chưa setup TXT record
+ Một cách khác để kiểm tra SMTP port 25 có bị chặn không là  telnet outbound.mailhop.org 25 -> nếu failed là bị chặn. Khi bị chặn các email gửi ra ngoài domain sẽ bị thông báo delay và sau đó là báo lỗi (bên dưới)
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#550 4.4.7 QUEUE.Expired; message expired ##
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+ Khi setup domain phải lưu ý setup cả rDNS (hay còn gọi là Reverse DNS) để hạn chế email bị từ chối hoặc rơi vào Spam. Thực hiện kiểm tra bằng các công cụ miễn phí ví dụ như http://www.dnsstuff.com/docs/ptr/. Xem kết quả bên dưới. Chỉ có ISP mới thực hiện được việc setup này (phải gọi điện y/c) -> nên thuê đường truyền + đăng ký domain từ 1 ISP để thực hiện dễ dàng hơn.
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IP Information - xxx.xxx.xxx.xxx IP address:                     xxx.xxx.xxx.xxx
Reverse DNS:                    xxx-xxx-xxx-fiber-net-static-ip.fpt.vn.
Reverse DNS authenticity:       [Could be forged: hostname xxx-xxx-xx-fiber-net-static-ip.fpt.vn. does not exist]
ASN:                            11111
ASN Name:                       FPT-AS-AP (The Corporation for Financing & Promoting Technology)
IP range connectivity:          7
Registrar (per ASN):            APNIC
Country (per IP registrar):     VN [Viet Nam]
Country Currency:               Unknown
Country IP Range:               210.245.0.0 to 210.245.127.255
Country fraud profile:          Normal
City (per outside source):      Unknown
Country (per outside source):   -- []
Private (internal) IP?          No
IP address registrar:           whois.apnic.net
Known Proxy?                    No
Link for WHOIS:                 xxx.xxx.xxx.xxx
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