There are several possible causes. 

Symptoms

An attempt to send a test E-mail notification fails with the following error message:

Mail server error

Cause

There are several possible reasons:

• A Firewall or your provider blocks the outgoing SMTP connection;
• The connection is lost while sending an E-mail;
• Not all of the E-mail settings were entered correctly

Solution

1. Make sure all the E-mail settings are correct and up-to-date.

Examples of settings for some email servers:

Gmail

1. In your Gmail settings turn on Access for less secure apps:
   
2. In Acronis True Image settings specify in this order:
   1. SMTP server: smtp.gmail.com
   2. Encryption: TLS
   3. Port: 587

   It is important to select the encryption type first, and then specify the port.

3. In the SMTP authentication section specify your Gmail e-mail address and password.
   

T-online Mail

T-online Mail
Outgoing mail server: securesmtp.t-online.de
Port: 587
Encryption: TLS
Username: your T-online e-mail address
Password: your T-online e-mail password

2. Make sure your Firewall does not block your outgoing network connections via the selected SMTP server port. Make sure your Firewall does not block the TrueImage.exe process;
3. Check that your network provider does not block your outgoing network connections via the selected port. You can use telnet to check this. See Using telnet to Test Open Ports;
4. Check if your e-mail provider offers alternative SMTP servers or different ports. If yes, try using these alternative settings;
5. Check your network connection and network access to the SMTP server. For example, do this with the ping command:
   • Open Start menu, type cmd and press Enter to open Command Prompt
   • In Command prompt, type ping <SMTP server address> and press Enter;
   • Check if there are any errors reaching SMTP server

More information

This error can also occur if your computer's name contains special symbols such as _ & #. Change computer name and remove these symbols to solve the issue.