Just a small note on the work of web forms, which I often forget about.
If you specify a gmail delivery address in the web forms and also the sender's letter is from gmail, then the letters will not reach. This is due to the fact that the mail server cannot match the server that sent the letter with the sender of the gmail. For the solution, it would be best to set the sender's address - the domain e-mail address.
However, this may not always help either, in my case I had to install a module for sending via smtp and MUST fill in the values SMTP client settings hostname and SMTP HELO/EHLO.