Header issue when sending an email

Describe the bug

Hello, I am using the latest version of the Watchtower image. I have configured email sending with a Google Workspace setup. The problem is that Google blocks connections with a HELO localhost header. I need to be able to replace it with something else, such as a domain name. Is it possible to add this feature? The parameters provided are correct because I use them for sending mail via phpMailer. Thank you.

Steps to reproduce

Configure email sending with Google
Launch watchtower in debug mode
Check the logs
You should see an error like: watchtower | time="2024-09-17T15:54:00Z" level=error msg="Failed to send shoutrrr notification" error="error enabling StartTLS: 421 4.7.0 Try again later, closing connection. (EHLO)\n4.7.0 For more information, go to\n4.7.0 https://support.google.com/a/answer/3221692 a640c23a62f3a-a90610f5d31sm14603366b.104 - gsmtp" index=0 notify=no service=smtp

Expected behavior

Receive an email on my email address without errors in the log

Screenshots

No response

Environment

Platform: debian 12
Architecture: x64
Docker Version: 27.2.1

Your logs

watchtower    | time="2024-09-17T15:53:54Z" level=trace msg="created Shoutrrr URL from legacy notifier" URL="smtp://sender%40example.com:password@smtp-relay.gmail.com:587/?auth=Plain&fromaddress=sender%40example.com&fromname=Watchtower&subject=&toaddresses=myadress%40example.com"    
watchtower    | time="2024-09-17T15:53:54Z" level=debug msg="Sleeping for a second to ensure the docker api client has been properly initialized."          
watchtower    | time="2024-09-17T15:53:55Z" level=debug msg="Making sure everything is sane before starting"                                                
watchtower    | time="2024-09-17T15:53:55Z" level=debug msg="Retrieving running containers"                                                                 
watchtower    | time="2024-09-17T15:53:55Z" level=debug msg="There are no additional watchtower containers"                                                 
watchtower    | time="2024-09-17T15:53:55Z" level=debug msg="Watchtower HTTP API skipped."                                                                  
watchtower    | time="2024-09-17T15:53:55Z" level=info msg="Watchtower 1.7.1"                                                                               
watchtower    | time="2024-09-17T15:53:55Z" level=info msg="Using notifications: smtp"                                                                      
watchtower    | time="2024-09-17T15:53:55Z" level=info msg="Checking all containers (except explicitly disabled with label)"                                
watchtower    | time="2024-09-17T15:53:55Z" level=info msg="Scheduling first run: 2024-09-18 15:53:55 +0000 UTC"                                            
watchtower    | time="2024-09-17T15:53:55Z" level=info msg="Note that the first check will be performed in 23 hours, 59 minutes, 59 seconds"                
watchtower    | time="2024-09-17T15:53:55Z" level=warning msg="Trace level enabled: log will include sensitive information as credentials and tokens"       
watchtower    | time="2024-09-17T15:53:58Z" level=error msg="Failed to send shoutrrr notification" error="error enabling StartTLS: 421 4.7.0 Try again later, closing connection. (EHLO)\n4.7.0  For more information, go to\n4.7.0  https://support.google.com/a/answer/3221692 a640c23a62f3a-a9061099278sm14502366b.34 - gsmtp" index=0 notify=no service=smtp                                                                                                                    
watchtower    | time="2024-09-17T15:54:00Z" level=error msg="Failed to send shoutrrr notification" error="error enabling StartTLS: 421 4.7.0 Try again later, closing connection. (EHLO)\n4.7.0  For more information, go to\n4.7.0  https://support.google.com/a/answer/3221692 a640c23a62f3a-a90610f5d31sm14603366b.104 - gsmtp" index=0 notify=no service=smtp

Additional context