Fix grammatical errors in email delivery document

Author: Cloud-Writer

Exchange/ExchangeOnline/antispam-and-protection/cannot-send-emails-to-external-recipients.md

@@ -23,32 +23,32 @@ _Original KB number:_   3019655
 
 ## Symptoms
 
-When users try to send mail from Microsoft 365 to an external recipient, the destination message transfer agent (MTA) rejects the message. The error message that users receive may vary. Typically, it states that the source server's host name does not match its IP address.
+When users try to send mail from Microsoft 365 to an external recipient, the destination message transfer agent (MTA) rejects the message. The error message that users receive may vary. Typically, it states that the source server's host name doesn't match its IP address.
 
 ## Cause
 
-The recipient server requires that the server name that's contained in the message HELO string have a corresponding pointer (PTR) resource record (reverse IP lookup). Microsoft 365 use multiple IP addresses to send mail. Because of DNS limitations, all these IP addresses can't be mapped through the PTR record to the server name that's in the message HELO string.
+The recipient server requires that the server name that's contained in the message HELO string have a corresponding pointer (PTR) resource record (reverse IP lookup). Microsoft 365 uses multiple IP addresses to send mail. Because of DNS limitations, all these IP addresses can't be mapped through the PTR record to the server name that's in the message HELO string.
 
 ## Resolution
 
-The method in which Microsoft 365 send email by using multiple IP addresses is typical for most large mail systems and is by design. Contact the recipient system administrator for help.
+The method that Microsoft 365 uses to send email messages by using multiple IP addresses is standard for most large mail systems and is by design. Contact the recipient's system administrator for help.
 
 ## More information
 
-In Microsoft 365, outgoing email settings use specific patterns. It's important to be aware of these patterns if your recipient servers use PTR record lookups for validation. This is because they explain why messages that are sent from the service might be rejected. The patterns are as follows:
+In Microsoft 365, outgoing email settings use specific patterns. It's important to be aware of these patterns if your recipient servers use PTR record lookups for validation. This is because they explain why messages sent from the service might be rejected. The patterns are as follows:
 
-1. The sending IP addresses that are used by Microsoft 365 have forward-confirmed reverse DNS records. This means that each sending IP address has both a forward (name-to-IP address) and a reverse (address-to-name) DNS record that contains matching information. For example:
+1. The sending IP addresses used by Microsoft 365 have forward-confirmed reverse DNS records. This means that each sending IP address has both a forward (name-to-IP address) and a reverse (address-to-name) DNS record that contains matching information. For example:
 
     ```console
     Outbound IP address: 157.56.110.65
     PTR record: 157.56.110.65 = mail-bn1on0065.outbound.protection.outlook.com
     A-record : mail-bn1on0065.outbound.protection.outlook.com = 157.56.110.65
     ```
 
-2. The HELO/EHLO strings that are used to identify the mail servers that are used by the service also contain `outbound.protection.outlook.com`. For example:  
+2. The HELO/EHLO strings which identify the mail servers that the Microsoft 365 service uses also contain `outbound.protection.outlook.com`. For example:  
    `na01-bn1-obe.outbound.protection.outlook.com`
 
-    All these HELO/EHLO strings have A records that contain some outgoing IP addresses that correspond to the sending mail servers. (However, the A records do not contain all these outgoing IP addresses.) For example:  
+    All these HELO/EHLO strings have A records that contain some outgoing IP addresses that correspond to the sending mail servers. However, the A records don't contain all these outgoing IP addresses. For example:  
     `HELO na01-bn1-obe.outbound.protection.outlook.com`
 
     A record: `na01-bn1-obe.outbound.protection.outlook.com`:
@@ -64,9 +64,9 @@ In Microsoft 365, outgoing email settings use specific patterns. It's important
     207.46.163.158  
     207.46.163.149
 
-3. The PTR records of the IP addresses in the A record of the EHLO/HELO string will not match the HELO/EHLO string of the sending mail server. For example:  
+3. The PTR records of the IP addresses in the A record of the EHLO/HELO string won't match the HELO/EHLO string of the sending mail server. For example:  
    PTR record: 207.46.163.150: `mail-bn1lp0150.outbound.protection.outlook.com`
 
-   Notice that `mail-bn1lp0150.outbound.protection.outlook.com` does not match `na01-bn1-obe.outbound.protection.outlook.com`.
+   Notice that `mail-bn1lp0150.outbound.protection.outlook.com` doesn't match `na01-bn1-obe.outbound.protection.outlook.com`.
 
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