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The best SMTP details to use when configuring an SMTP plugin within WordPress when you're using CreateTheWeb WordPress hosting are:
Outgoing mail server: smtp.stackmail.com.
Outgoing server port (SMTP): 465
Use the following type of encrypted connection: TLS (or SSL/TLS)
Using these details will allow emails to be sent via SMTP from WordPress forms or allow any other SMTP-based plugins to send.