Attachment scanning on email servers is an advanced security process that hosting providers must implement to ensure safety and integrity of emails being sent and received. Let's delve deeper into the key components, benefits, and challenges of this system.

1. Understanding Email Attachment Scanning 
Email attachment scanning is the process of automatically inspecting files attached to emails, using a combination of antivirus, antimalware, and sometimes advanced AI techniques. The hosting provider's server checks each attachment as the email arrives, ensuring that potential threats are filtered out before they reach the users inbox. This reduces the risk of malware, ransomware, and phishing attacks reaching end users.

2. Security Techniques Used in Scanning 
Attachment scanning relies on multiple layers of security protocols, including:

• Signature-based detection: This checks the attachment against a database of known malware and viruses. If the file matches a known signature, it's flagged as malicious.
  
• Behavioral analysis: Instead of just relying on known signatures, this method looks for suspicious behavior in the file, like unexpected file modifications or attempts to access system files.
  
• Machine learning: Advanced email servers use AI to identify new types of malware by analyzing large datasets of email traffic and spotting unusual trends or behaviors.
  

These methods help to identify both known and unknown threats, ensuring that even sophisticated attacks have a lower chance of succes.

3. Why is Attachment Scanning Important for Hosting? 
Hosting providers need to protect not only their users but also their servers from malware infections, ransomware, and data breaches. A compromised email server can lead to mass infections and severely damage the provider's reputation. Furthermore, unchecked malware can be passed from one user to another, spreading like wildfire.

4. Regulatory Compliance and Attachment Scanning 
With strict privacy regulations like GDPR, HIPAA, and others, hosting providers have legal obligations to ensure that sensitive data is protected at all times. Email attachment scanning plays a vital role in ensuring compliance with these regulations, reducing the risk of data leaks, cyberattacks, and regulatory fines.

5. Types of Files Scanned 
Common file types like PDFs, Word dоcuments, Excel spreadsheets, and ZIP files are most frequently targeted for scanning, as these are often exploited by attackers to hide malware. However, the server should also be capable of scanning less common formats, as cybercriminals often take advantage of files that may not get scrutinized as thoroughly.

6. Challenges and Limitations 
While scanning is highly effective, there are challenges that hosting providers face. 

• False positives: Sometimes, safe attachments are mistakenly flagged as harmful, leading to frustration among users who may not receive important emails in a timely manner.
  
• Increased resource usage: Scanning large attachments or numerous attachments in high volumes of emails can strain server resources, slowing down performance.
  
• Encrypted attachments: If an attachment is encrypted, the server may be unable to scan it, as it lacks the decryption key, which can allow harmful files to slip through.
  

Balancing security and performance is key to making attachment scanning effective without negatively impacting the user experince.

7. Best Practices for Hosting Providers 
To maintain high standards of email attachment security, hosting providers should follow these best practices:

• Regularly update virus definitions and scanning software to catch the latest threats.
• Monitor server performance to avoid bottlenecks caused by scanning processes.
• Offer customers the ability to manually approve or reject flagged attachments.
• Use multi-layered security, combining attachment scanning with other measures like firewalls and email encryption.

Email server attachment scanning is a crucial feature for hosting providers, offering a vital layer of protection against growing cyberthreats. By staying updated on the latest security trends and refining their scanning systems, hosting providers can deliver both safety and reliability to their customers.