Can I manually mark emails to be part of the same conversation?

Several emails in my Outlook.com account appear as separate conversations even though they are actually replies to earlier emails. Everything appears as though Outlook.com should detect that they are the one conversation (i.e. same subject, contain original email, etc.). Most of the emails this applies to are ones that I imported from Gmail, but some are emails that I sent/received in Outlook.com.

Possible solutions to this would be:

• if I could manually mark the emails and select a "merge to conversation" option or similar;
• if there was an option to force Outlook.com to recheck all emails to see if they are a conversation;
• if someone could provide details of how Outlook.com determines if emails are part of the same conversation and I might be able to manually edit the emails to make Outlook.com recognise that they are the same conversation.

Thanks in advance for any help that people might be able to provide.