[quote user="aderoy"]

You can create a search by date across all folders.

Menu Edit | Find Text | Message Age

 This will then create a folder with links to all the messages. If you have the option  set to deleting Link from from a Link folder also deletes original you should be able to do as you wish

Menu Tools | Options | Incoming mail | Folder behaviours  last two check boxes.

[/quote]

Thanks a lot! Worked like a charm!

I have a large folder structure in Pegasus Mail with email messages from the beginning, more than 20 years ago, until today.
Now I decided that I don’t need messages older than 5 years anymore.
How can I delete all messages from all folders that are older than 5 years?

You can create a general rule set using message age or date and tell the rule to delete messages that match your criteria. Attach the rule set to each folder then open the folders one by one. As always, take a backup of your data before starting this in case it does not work as expected.

You can create a search by date across all folders.

Menu Edit | Find Text | Message Age

 This will then create a folder with links to all the messages. If you have the option  set to deleting Link from from a Link folder also deletes original you should be able to do as you wish

Menu Tools | Options | Incoming mail | Folder behaviours  last two check boxes.

hth 

[quote user="Greenman"]

You can create a general rule set using

message age or date and tell the rule to delete messages that match your

criteria. Attach the rule set to each folder then open the folders one

by one. As always, take a backup of your data before starting this in

case it does not work as expected.

[/quote]

 Thanks, but that's still a lot of work with a huge amount of folders.

[quote user="allgaeu-tobias"]...

 Thanks, but that's still a lot of work with a huge amount of folders.

[/quote]

aderoy's much better suggestion should work for you.